Ebola Virus (3)
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Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a
viral hemorrhagic fever Viral hemorrhagic fevers (VHFs) are a diverse group of diseases. "Viral" means a health problem caused by infection from a virus, " hemorrhagic" means to bleed, and "fever" means an unusually high body temperature. Bleeding and fever are comm ...
in humans and other
primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...
s, caused by
ebolavirus The genus ''Ebolavirus'' (- or ; - or ) is a International Committee on Taxonomy of Viruses, virological taxon included in the family ''Filoviridae'' (filament-shaped viruses), order ''Mononegavirales''. The members of this genus are called ebo ...
es. Symptoms typically start anywhere between two days and three weeks after infection. The first symptoms are usually
fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...
,
sore throat Sore throat, also known as throat pain, is pain or irritation of the throat. The majority of sore throats are caused by a virus, for which antibiotics are not helpful. For sore throat caused by bacteria (GAS), treatment with antibiotics may hel ...
,
muscle pain Myalgia or muscle pain is a painful sensation evolving from muscle tissue. It is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another likely cause is viral infection, espec ...
, and
headache A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe ...
s. These are usually followed by
vomiting Vomiting (also known as emesis, puking and throwing up) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteritis, pre ...
,
diarrhoea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...
,
rash A rash is a change of the skin that affects its color, appearance, or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracke ...
and decreased
liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...
and
kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...
function, at which point some people begin to bleed both internally and externally. It kills between 25% and 90% of those infected – about 50% on average. Death is often due to shock from fluid loss, and typically occurs between 6 and 16 days after the first symptoms appear. Early treatment of symptoms increases the survival rate considerably compared to late start.Ebola in Uganda: An
Ebola vaccine Ebola vaccines are vaccines either approved or in development to prevent Ebola. As of 2022, there are only vaccines against the Zaire ebolavirus. The first vaccine to be approved in the United States was rVSV-ZEBOV in December 2019. It had ...
was approved by the US FDA in December 2019. The virus spreads through direct contact with
body fluid Body fluids, bodily fluids, or biofluids, sometimes body liquids, are liquids within the Body (biology), body of an organism. In lean healthy adult men, the total body water is about 60% (60–67%) of the total Human body weight, body weight; it ...
s, such as
blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood is com ...
from infected humans or other animals, or from contact with items that have recently been contaminated with infected body fluids. There have been no documented cases, either in nature or under laboratory conditions, of spread through the air between humans or other
primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...
s. After recovering from Ebola,
semen Semen, also known as seminal fluid, is a bodily fluid that contains spermatozoon, spermatozoa which is secreted by the male gonads (sexual glands) and other sexual organs of male or hermaphrodite, hermaphroditic animals. In humans and placen ...
or
breast milk Breast milk (sometimes spelled as breastmilk) or mother's milk is milk produced by the mammary glands in the breasts of women. Breast milk is the primary source of nutrition for newborn infants, comprising fats, proteins, carbohydrates, and a var ...
may continue to carry the virus for anywhere between several weeks to several months.
Fruit bat Megabats constitute the family Pteropodidae of the order Chiroptera. They are also called fruit bats, Old World fruit bats, or—especially the genera ''Acerodon'' and ''Pteropus''—flying foxes. They are the only member of the superfamil ...
s are believed to be the normal carrier in nature; they are able to spread the virus without being affected by it. The symptoms of Ebola may resemble those of several other diseases, including
malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...
,
cholera Cholera () is an infection of the small intestine by some Strain (biology), strains of the Bacteria, bacterium ''Vibrio cholerae''. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea last ...
,
typhoid fever Typhoid fever, also known simply as typhoid, is a disease caused by '' Salmonella enterica'' serotype Typhi bacteria, also called ''Salmonella'' Typhi. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often th ...
,
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasion ...
and other viral hemorrhagic fevers. Diagnosis is confirmed by testing blood samples for the presence of viral
RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...
, viral
antibodies An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...
or the virus itself. Control of outbreaks requires coordinated medical services and community engagement, including rapid detection,
contact tracing In public health, contact tracing is the process of identifying people who may have been exposed to an infected person ("contacts") and subsequent collection of further data to assess transmission. By tracing the contacts of infected individua ...
of those exposed, quick access to laboratory services, care for those infected, and proper disposal of the dead through
cremation Cremation is a method of Disposal of human corpses, final disposition of a corpse through Combustion, burning. Cremation may serve as a funeral or post-funeral rite and as an alternative to burial. In some countries, including India, Nepal, and ...
or burial. Prevention measures involve wearing proper protective clothing and
washing hands Hand washing (or handwashing), also known as hand hygiene, is the act of cleaning one's hands with soap or handwash and water to remove viruses, bacteria, microorganisms, dirt, grease, and other harmful or unwanted substances stuck to the han ...
when in close proximity to patients and while handling potentially infected
bushmeat Bushmeat is meat from wildlife species that are Hunting, hunted for human consumption. Bushmeat represents a primary source of animal protein and a cash-earning commodity in poor and rural communities of humid tropical forest regions of the worl ...
, as well as thoroughly cooking bushmeat. An
Ebola vaccine Ebola vaccines are vaccines either approved or in development to prevent Ebola. As of 2022, there are only vaccines against the Zaire ebolavirus. The first vaccine to be approved in the United States was rVSV-ZEBOV in December 2019. It had ...
was approved by the US FDA in December 2019. While there is no approved treatment for Ebola , two treatments (
atoltivimab/maftivimab/odesivimab Atoltivimab/maftivimab/odesivimab, sold under the brand name INMAZEB, is a fixed-dose combination of three monoclonal antibodies for the treatment of ''Zaire ebolavirus'' (Ebola virus). It was developed by Regeneron Pharmaceuticals and contain ...
and ansuvimab) are associated with improved outcomes. Supportive efforts also improve outcomes. These include
oral rehydration therapy Oral rehydration therapy (ORT) also officially known as Oral Rehydration Solution is a type of fluid replacement used to prevent and treat dehydration, especially due to diarrhea. It involves drinking water with modest amounts of sugar and salt ...
(drinking slightly sweetened and salty water) or giving
intravenous fluids Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...
, and treating symptoms. In October 2020, atoltivimab/maftivimab/odesivimab (Inmazeb) was approved for medical use in the United States to treat the disease caused by ''Zaire ebolavirus''.


History and name

Ebola was first identified in 1976, in two simultaneous outbreaks, one in Nzara (a town in
South Sudan South Sudan (), officially the Republic of South Sudan, is a landlocked country in East Africa. It is bordered on the north by Sudan; on the east by Ethiopia; on the south by the Democratic Republic of the Congo, Uganda and Kenya; and on the ...
) and the other in
Yambuku Yambuku is a small village in Mongala, Mongala Province in northern Democratic Republic of the Congo. It was the center of the first documented outbreak of Ebola, Ebola virus disease, in 1976, with the World Health Organization identifying a man fr ...
(
the Democratic Republic of the Congo The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...
), a village near the
Ebola River The Ebola River ( or ), also commonly known by its Ngbandi name Legbala, is the headstream of the Mongala River, a tributary of the Congo River, in northern Democratic Republic of the Congo. It is roughly in length. The name ''Ebola'' is a Fre ...
, for which the disease was named. Ebola outbreaks occur intermittently in tropical regions of
sub-Saharan Africa Sub-Saharan Africa is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern Africa, and West Africa. Geopolitically, in addition to the list of sovereign states and ...
. Between 1976 and 2012, according to the
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
, there were 24 outbreaks of Ebola resulting in a total of 2,387 cases, and 1,590 deaths. The largest Ebola outbreak to date was an epidemic in West Africa from December 2013 to January 2016, with cases and deaths. On 29 March 2016, it was declared to no longer be an emergency. Other outbreaks in Africa began in the Democratic Republic of the Congo in May 2017, and 2018. In July 2019, the World Health Organization declared the Congo Ebola outbreak a world health emergency.


Signs and symptoms


Onset

The length of time between exposure to the virus and the development of symptoms (
incubation period Incubation period (also known as the latent period or latency period) is the time elapsed between exposure to a pathogenic organism, a chemical, or ionizing radiation, radiation, and when symptoms and signs are first apparent. In a typical infect ...
) is between 2 and 21 days, and usually between 4 and 10 days. However, recent estimates based on mathematical models predict that around 5% of cases may take longer than 21 days to develop. Symptoms usually begin with a sudden
influenza Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These sympto ...
-like stage characterised by
fatigue Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself. Fatigue (in the medical sense) is sometimes associated wit ...
,
fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...
,
weakness Weakness is a symptom of many different medical conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, ...
,
decreased appetite Anorexia is a medical term for a loss of appetite. While the term outside of the scientific literature is often used interchangeably with anorexia nervosa, many possible causes exist for a loss of appetite, some of which may be harmless, while o ...
,
muscular pain Myalgia or muscle pain is a painful sensation evolving from muscle tissue. It is a symptom of many diseases. The most common cause of acute (medicine), acute myalgia is the overuse of a muscle or Muscle group, group of muscles; another likely c ...
,
joint pain Arthralgia () literally means 'joint pain'. Specifically, arthralgia is a symptom of injury, infection, illness (in particular arthritis), or an allergic reaction to medication Medication (also called medicament, medicine, pharmaceutic ...
, headache, and sore throat. The fever is usually higher than . This is often followed by nausea, vomiting,
diarrhoea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...
, abdominal pain, and sometimes
hiccups A hiccup (scientific name singultus, from Latin for "sob, hiccup"; also spelled hiccough) is an involuntary contraction ( myoclonic jerk) of the diaphragm that may repeat several times per minute. The hiccup is an involuntary action involvi ...
. The combination of severe vomiting and diarrhoea often leads to severe
dehydration In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild deh ...
. Next,
shortness of breath Shortness of breath (SOB), known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing discomfort that con ...
and
chest pain Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp, dull, pressure, heaviness or squeezing. Associated symptoms may include pain in the shoulder, arm, upper abdomen, or jaw, along with n ...
may occur, along with swelling,
headaches A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Head ...
, and
confusion In psychology, confusion is the quality or emotional state of being bewildered or unclear. The term "acute mental confusion"
. In about half of the cases, the skin may develop a
maculopapular rash A maculopapular rash is a type of rash characterized by a flat, red area on the skin that is covered with small confluent bumps. It may only appear red in lighter-skinned people. The term "maculopapular" is a compound: '' macules'' are small, fla ...
, a flat red area covered with small bumps, five to seven days after symptoms begin.


Bleeding

In some cases, internal and external bleeding may occur. This typically begins five to seven days after the first symptoms. All infected people show some decreased blood clotting. Bleeding from mucous membranes or from sites of needle punctures has been reported in 40–50% of cases. This may cause
vomiting blood Hematemesis is the vomiting of blood. It can be confused with hemoptysis (coughing up blood) or Nosebleed, epistaxis (nosebleed), which are more common. The source is generally the upper gastrointestinal tract, typically above the suspensory mus ...
, coughing up of blood, or
blood in stool Blood in stool looks different depending on how early it enters the digestive tract—and thus how much digestive action it has been exposed to—and how much there is. The term can refer either to melena, with a black appearance, typically or ...
. Bleeding into the skin may create
petechia A petechia (; : petechiae) is a small red or purple spot ( 1 cm in diameter) and purpura (3 to 10 mm in diameter). The term is typically used in the plural (petechiae), since a single petechia is seldom noticed or significant. Causes Physical t ...
e,
purpura Purpura () is a condition of red or purple discolored spots on the skin that do not blanch on applying pressure. The spots are caused by bleeding underneath the skin secondary to platelet disorders, vascular disorders, coagulation disorders, ...
,
ecchymoses A bruise, also known as a contusion, is a type of hematoma of tissue, the most common cause being capillaries damaged by trauma, causing localized bleeding that extravasates into the surrounding interstitial tissues. Most bruises occur c ...
or
haematoma A hematoma, also spelled haematoma, or blood suffusion is a localized bleeding outside of blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. A hematoma is ...
s (especially around needle injection sites). Bleeding into the whites of the eyes may also occur. Heavy bleeding is uncommon; if it occurs, it is usually in the
gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...
. The incidence of bleeding into the gastrointestinal tract was reported to be ~58% in the 2001 outbreak in Gabon, but in the 2014–15 outbreak in the US it was ~18%, possibly due to improved prevention of
disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking Microvessel, small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems ...
.


Recovery or death

Recovery may begin between seven and 14 days after first symptoms. Death, if it occurs, follows typically six to sixteen days from first symptoms and is often due to shock from fluid loss. In general, bleeding often indicates a worse outcome, and blood loss may result in death. People are often in a
coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to Nociception, respond normally to Pain, painful stimuli, light, or sound, lacks a normal Circadian rhythm, sleep-wake cycle and does not initiate ...
near the end of life. Those who survive often have ongoing muscular and joint pain, liver inflammation, and decreased hearing, and may have continued tiredness, continued weakness, decreased appetite, and difficulty returning to pre-illness weight. Problems with vision may develop. It is recommended that survivors of EVD wear condoms for at least twelve months after initial infection or until the semen of a male survivor tests negative for Ebola virus on two separate occasions. Survivors develop
antibodies An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...
against Ebola that last at least 10 years, but it is unclear whether they are immune to additional infections.


Cause

EVD in humans is caused by four of six viruses of the genus ''
Ebolavirus The genus ''Ebolavirus'' (- or ; - or ) is a International Committee on Taxonomy of Viruses, virological taxon included in the family ''Filoviridae'' (filament-shaped viruses), order ''Mononegavirales''. The members of this genus are called ebo ...
''. The four are
Bundibugyo virus The species ''Bundibugyo ebolavirus'' ( ) is the taxonomic home of one virus, Bundibugyo virus (BDBV), that forms filamentous virions and is closely related to the infamous Ebola virus (EBOV). The virus causes severe disease in humans in the form ...
(BDBV), Sudan virus (SUDV), Taï Forest virus (TAFV) and one simply called
Ebola virus ''Orthoebolavirus zairense'' or Zaire ebolavirus, more commonly known as Ebola virus (; EBOV), is one of six known species within the genus ''Ebolavirus''. Four of the six known ebolaviruses, including EBOV, cause a severe and often fatal vira ...
(EBOV, formerly Zaire Ebola virus). EBOV, species ''
Zaire ebolavirus ''Orthoebolavirus zairense'' or Zaire ebolavirus, more commonly known as Ebola virus (; EBOV), is one of six known species within the genus ''Ebolavirus''. Four of the six known ebolaviruses, including EBOV, cause a severe and often fatal hem ...
'', is the most dangerous of the known EVD-causing viruses, and is responsible for the largest number of outbreaks. The fifth and sixth viruses,
Reston virus Reston virus (RESTV) is one of six known viruses within the genus ''Ebolavirus''. Reston virus causes Ebola virus disease in non-human primates; out of all 6 ebolaviruses, it is one of the only two not known to cause disease in humans, but has ca ...
(RESTV) and Bombali virus (BOMV), are not thought to cause disease in humans, but have caused disease in other primates. All six viruses are closely related to
marburgvirus The genus ''Marburgvirus'' is the taxonomic home of ''Marburg marburgvirus'', whose members are the two known marburgviruses, Marburg virus (MARV) and Ravn virus (RAVV). Both viruses cause Marburg virus disease in humans and nonhuman primat ...
es.


Virology

Ebolaviruses contain single-stranded, non-infectious
RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...
genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...
s. ''Ebolavirus'' genomes contain seven
gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
s including 3'-UTR-''NP''-''VP35''-''VP40''-''GP''-''VP30''-''VP24''-''L''- 5'-UTR. The genomes of the five different ebolaviruses (BDBV, EBOV, RESTV, SUDV and TAFV) differ in
sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is cal ...
and the number and location of gene overlaps. As with all
filovirus ''Filoviridae'' () is a family of single-stranded negative-sense RNA viruses in the order ''Mononegavirales''. Two members of the family that are commonly known are Ebola virus and Marburg virus. Both viruses, and some of their lesser known rela ...
es, ebolavirus virions are filamentous particles that may appear in the shape of a shepherd's crook, of a "U" or of a "6," and they may be coiled, toroid or branched. In general, ebolavirions are 80 nanometers (nm) in width and may be as long as 14,000 nm. Their
life cycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia *Biological life cycle, the sequence of life stages that an organism undergoes from conception to reproduction *Life-cycle hypothesis, in economics *Erikson's stages of psy ...
is thought to begin with a virion attaching to specific cell-surface receptors such as
C-type lectin A C-type lectin (CLEC) is a type of carbohydrate-binding protein known as a lectin. The C-type designation is from their requirement for calcium for binding. Proteins that contain C-type lectin domains have a diverse range of functions including c ...
s,
DC-SIGN DC-SIGN (Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin) also known as CD209 ( Cluster of Differentiation 209) is a protein which in humans is encoded by the ''CD209'' gene. DC-SIGN is a C-type lectin receptor p ...
, or
integrin Integrins are transmembrane receptors that help cell–cell and cell–extracellular matrix (ECM) adhesion. Upon ligand binding, integrins activate signal transduction pathways that mediate cellular signals such as regulation of the cell cycle, o ...
s, which is followed by fusion of the viral envelope with cellular membranes. The virions taken up by the cell then travel to acidic
endosome Endosomes are a collection of intracellular sorting organelles in eukaryotic cells. They are parts of the endocytic membrane transport pathway originating from the trans Golgi network. Molecules or ligands internalized from the plasma membra ...
s and
lysosome A lysosome () is a membrane-bound organelle that is found in all mammalian cells, with the exception of red blood cells (erythrocytes). There are normally hundreds of lysosomes in the cytosol, where they function as the cell’s degradation cent ...
s where the viral envelope glycoprotein GP is cleaved. This processing appears to allow the virus to bind to cellular proteins enabling it to fuse with internal cellular membranes and release the viral
nucleocapsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or ma ...
. The ''Ebolavirus'' structural glycoprotein (known as GP1,2) is responsible for the virus' ability to bind to and infect targeted cells. The viral
RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that catalyzes the chemical reactions that synthesize RNA from a DNA template. Using the e ...
, encoded by the ''L'' gene, partially uncoats the nucleocapsid and transcribes the genes into positive-strand
mRNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein. mRNA is ...
s, which are then
translated Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...
into structural and nonstructural proteins. The most abundant protein produced is the nucleoprotein, whose concentration in the host cell determines when L switches from gene transcription to genome replication. Replication of the viral genome results in full-length, positive-strand antigenomes that are, in turn, transcribed into genome copies of negative-strand virus progeny. Newly synthesised structural proteins and genomes self-assemble and accumulate near the inside of the
cell membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...
. Virions
bud In botany, a bud is an undeveloped or Plant embryogenesis, embryonic Shoot (botany), shoot and normally occurs in the axil of a leaf or at the tip of a Plant stem, stem. Once formed, a bud may remain for some time in a dormancy, dormant conditi ...
off from the cell, gaining their envelopes from the cellular membrane from which they bud. The mature progeny particles then infect other cells to repeat the cycle. The genetics of the Ebola virus are difficult to study because of EBOV's virulent characteristics.


Transmission

It is believed that between people, Ebola disease spreads only by direct contact with the blood or other
body fluid Body fluids, bodily fluids, or biofluids, sometimes body liquids, are liquids within the Body (biology), body of an organism. In lean healthy adult men, the total body water is about 60% (60–67%) of the total Human body weight, body weight; it ...
s of a person who has developed symptoms of the disease. Body fluids that may contain Ebola viruses include saliva, mucus, vomit, feces, sweat, tears, breast milk, urine and
semen Semen, also known as seminal fluid, is a bodily fluid that contains spermatozoon, spermatozoa which is secreted by the male gonads (sexual glands) and other sexual organs of male or hermaphrodite, hermaphroditic animals. In humans and placen ...
. The WHO states that only people who are very sick are able to spread Ebola disease in
saliva Saliva (commonly referred as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which ...
, and the virus has not been reported to be transmitted through sweat. Most people spread the virus through blood,
feces Feces (also known as faeces American and British English spelling differences#ae and oe, or fæces; : faex) are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the ...
and vomit. Entry points for the virus include the nose, mouth, eyes, open wounds, cuts and abrasions. Ebola may be spread through large
droplets A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the end of a tube or other surface boundary, producing a hanging drop called a pendant drop. Dro ...
; however, this is believed to occur only when a person is very sick. This contamination can happen if a person is splashed with droplets. Contact with surfaces or objects contaminated by the virus, particularly needles and syringes, may also transmit the infection. The virus is able to survive on objects for a few hours in a dried state, and can survive for a few days within body fluids outside of a person. The Ebola virus may be able to persist for more than three months in the semen after recovery, which could lead to infections via
sexual intercourse Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the Erection, erect male Human penis, penis inside the female vagina and followed by Pelvic thrust, thrusting motions for sexual pleasure ...
. Virus persistence in semen for over a year has been recorded in a national screening programme. Ebola may also occur in the breast milk of women after recovery, and it is not known when it is safe to breastfeed again. The virus was also found in the eye of one patient, in 2014, two months after it was cleared from his blood. Otherwise, people who have recovered are not infectious. The potential for widespread infections in countries with medical systems capable of observing correct medical isolation procedures is considered low. Usually when someone has symptoms of the disease, they are unable to travel without assistance. Dead bodies remain infectious; thus, people handling human remains in practices such as traditional burial rituals or more modern processes such as
embalming Embalming is the art and science of preserving human remains by treating them with embalming chemicals in modern times to forestall decomposition. This is usually done to make the deceased suitable for viewing as part of the funeral ceremony or ...
are at risk. Of the cases of Ebola infections in Guinea during the 2014 outbreak, 69% are believed to have been contracted via unprotected (or unsuitably protected) contact with infected corpses during certain Guinean burial rituals. Health-care workers treating people with Ebola are at greatest risk of infection. The risk increases when they do not have appropriate protective clothing such as masks, gowns, gloves and eye protection; do not wear it properly; or handle contaminated clothing incorrectly. This risk is particularly common in parts of Africa where the disease mostly occurs and health systems function poorly. There has been transmission in hospitals in some African countries that reuse hypodermic needles. Some health-care centres caring for people with the disease do not have running water. In the United States the spread to two medical workers treating infected patients prompted criticism of inadequate training and procedures. Human-to-human transmission of EBOV through the air has not been reported to occur during EVD outbreaks, and airborne transmission has only been demonstrated in very strict laboratory conditions, and then only from pigs to
primates Primates is an order of mammals, which is further divided into the strepsirrhines, which include lemurs, galagos, and lorisids; and the haplorhines, which include tarsiers and simians ( monkeys and apes). Primates arose 74–63  ...
, but not from primates to primates. Spread of EBOV by water, or food other than bushmeat, has not been observed. No spread by mosquitos or other insects has been reported. Other possible methods of transmission are being studied. Airborne transmission among humans is theoretically possible due to the presence of Ebola virus particles in saliva, which can be discharged into the air with a cough or sneeze, but observational data from previous epidemics suggests the actual risk of airborne transmission is low. A number of studies examining airborne transmission broadly concluded that transmission from pigs to primates could happen without direct contact because, unlike humans and primates, pigs with EVD get very high ebolavirus concentrations in their lungs, and not their bloodstream. Therefore, pigs with EVD can spread the disease through droplets in the air or on the ground when they sneeze or cough. By contrast, humans and other primates accumulate the virus throughout their body and specifically in their blood, but not very much in their lungs. It is believed that this is the reason researchers have observed pig to primate transmission without physical contact, but no evidence has been found of primates being infected without actual contact, even in experiments where infected and uninfected primates shared the same air.


Initial case

Although it is not entirely clear how Ebola initially spreads from animals to humans, the spread is believed to involve direct contact with an infected wild animal or fruit bat. Besides bats, other wild animals that are sometimes infected with EBOV include several species of monkeys such as
baboon Baboons are primates comprising the biology, genus ''Papio'', one of the 23 genera of Old World monkeys, in the family Cercopithecidae. There are six species of baboon: the hamadryas baboon, the Guinea baboon, the olive baboon, the yellow ba ...
s,
great apes The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); '' Gorilla'' (the ...
(
chimpanzee The chimpanzee (; ''Pan troglodytes''), also simply known as the chimp, is a species of Hominidae, great ape native to the forests and savannahs of tropical Africa. It has four confirmed subspecies and a fifth proposed one. When its close rel ...
s and
gorilla Gorillas are primarily herbivorous, terrestrial great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four or five su ...
s), and
duikers A duiker is a small to medium-sized brown antelope native to sub-Saharan Africa, found in heavily wooded areas. The 22 extant species, including three sometimes considered to be subspecies of the other species, form the subfamily Cephalophinae ...
(a species of
antelope The term antelope refers to numerous extant or recently extinct species of the ruminant artiodactyl family Bovidae that are indigenous to most of Africa, India, the Middle East, Central Asia, and a small area of Eastern Europe. Antelopes do ...
). Animals may become infected when they eat fruit partially eaten by bats carrying the virus. Fruit production, animal behavior and other factors may trigger outbreaks among animal populations. Evidence indicates that both domestic dogs and pigs can also be infected with EBOV. Dogs do not appear to develop symptoms when they carry the virus, and pigs appear to be able to transmit the virus to at least some primates. Although some dogs in an area in which a human outbreak occurred had antibodies to EBOV, it is unclear whether they played a role in spreading the disease to people.


Reservoir

The
natural reservoir In Infection, infectious disease ecology and epidemiology, a natural reservoir, also known as a disease reservoir or a reservoir of infection, is the population of organisms or the specific environment in which an infectious pathogen naturally li ...
for Ebola has yet to be confirmed; however,
bat Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...
s are considered to be the most likely candidate. Three types of fruit bats ('' Hypsignathus monstrosus'', ''
Epomops franqueti Franquet's epauletted fruit bat (''Epomops franqueti'') is a species of megabat in the family Pteropodidae, and is one of three different species of epauletted bats. Franquet's epauletted fruit bat has a range of habitats, varying from Subsaharan ...
'' and ''
Myonycteris torquata ''Myonycteris'' (collared bat) is a genus of bat Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight tha ...
'') were found to possibly carry the virus without getting sick. , whether other animals are involved in its spread is not known. Plants,
arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s,
rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...
s, and birds have also been considered possible viral reservoirs. Bats were known to roost in the cotton factory in which the first cases of the 1976 and 1979 outbreaks were observed, and they have also been implicated in Marburg virus infections in 1975 and 1980. Of 24 plant and 19 vertebrate species experimentally inoculated with EBOV, only bats became infected. The bats displayed no clinical signs of disease, which is considered evidence that these bats are a reservoir species of EBOV. In a 2002–2003 survey of 1,030 animals including 679 bats from
Gabon Gabon ( ; ), officially the Gabonese Republic (), is a country on the Atlantic coast of Central Africa, on the equator, bordered by Equatorial Guinea to the northwest, Cameroon to the north, the Republic of the Congo to the east and south, and ...
and the
Republic of the Congo The Republic of the Congo, also known as Congo-Brazzaville, the Congo Republic or simply the Congo (the last ambiguously also referring to the neighbouring Democratic Republic of the Congo), is a country located on the western coast of Central ...
, immunoglobulin G (IgG) immune defense molecules indicative of Ebola infection were found in three bat species; at various periods of study, between 2.2 and 22.6% of bats were found to contain both RNA sequences and IgG molecules indicating Ebola infection. Antibodies against Zaire and Reston viruses have been found in fruit bats in
Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...
, suggesting that these bats are also potential hosts of the virus and that the filoviruses are present in Asia. Between 1976 and 1998, in 30,000 mammals, birds, reptiles, amphibians and
arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s sampled from regions of EBOV outbreaks, no Ebola virus was detected apart from some genetic traces found in six rodents (belonging to the species '' Mus setulosus'' and ''
Praomys ''Praomys'' is a genus of rodent in the family Muridae endemic to Sub-Saharan Africa Sub-Saharan Africa is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern A ...
'') and one
shrew Shrews ( family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to dif ...
('' Sylvisorex ollula'') collected from the
Central African Republic The Central African Republic (CAR) is a landlocked country in Central Africa. It is bordered by Chad to Central African Republic–Chad border, the north, Sudan to Central African Republic–Sudan border, the northeast, South Sudan to Central ...
. However, further research efforts have not confirmed rodents as a reservoir. Traces of EBOV were detected in the carcasses of gorillas and chimpanzees during outbreaks in 2001 and 2003, which later became the source of human infections. However, the high rates of death in these species resulting from EBOV infection make it unlikely that these species represent a natural reservoir for the virus.
Deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...
has been mentioned as a possible contributor to recent outbreaks, including the
West African Ebola virus epidemic The 2013–2016 epidemic of Ebola virus disease, centered in West Africa, was the most widespread outbreak of the disease in history. It caused major loss of life and socioeconomic disruption in the region, mainly in Guinea, Liberia and Sie ...
. Index cases of EVD have often been close to recently deforested lands.


Pathophysiology

Like other
filoviruses ''Filoviridae'' () is a family of single-stranded negative-sense RNA viruses in the order ''Mononegavirales''. Two members of the family that are commonly known are Ebola virus and Marburg virus. Both viruses, and some of their lesser known rela ...
, EBOV replicates very efficiently in many
cells Cell most often refers to: * Cell (biology), the functional basic unit of life * Cellphone, a phone connected to a cellular network * Clandestine cell, a penetration-resistant form of a secret or outlawed organization * Electrochemical cell, a d ...
, producing large amounts of virus in
monocyte Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and monocyte-derived dendritic cells. As a part of the vertebrate innate immune system monocytes also ...
s,
macrophage Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...
s,
dendritic cell A dendritic cell (DC) is an antigen-presenting cell (also known as an ''accessory cell'') of the mammalian immune system. A DC's main function is to process antigen material and present it on the cell surface to the T cells of the immune system ...
s and other cells including
liver cells A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass. These cells are involved in: * Protein synthesis * Protein storage * Transformation of carbohydrates * Synthesis of cholesterol, bile ...
,
fibroblast A fibroblast is a type of cell (biology), biological cell typically with a spindle shape that synthesizes the extracellular matrix and collagen, produces the structural framework (Stroma (tissue), stroma) for animal Tissue (biology), tissues, and ...
s, and adrenal gland cells. Viral replication triggers high levels of inflammatory chemical signals and leads to a septic state. EBOV is thought to infect humans through contact with mucous membranes or skin breaks. After infection,
endothelial cells The endothelium (: endothelia) is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the res ...
(cells lining the inside of blood vessels), liver cells, and several types of immune cells such as macrophages, monocytes, and dendritic cells are the main targets of attack. Following infection, immune cells carry the virus to nearby
lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...
s where further reproduction of the virus takes place. From there the virus can enter the bloodstream and
lymphatic system The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphoid organs, lympha ...
and spread throughout the body. Macrophages are the first cells infected with the virus, and this infection results in
programmed cell death Programmed cell death (PCD) sometimes referred to as cell, or cellular suicide is the death of a cell (biology), cell as a result of events inside of a cell, such as apoptosis or autophagy. PCD is carried out in a biological process, which usual ...
. Other types of
white blood cell White blood cells (scientific name leukocytes), also called immune cells or immunocytes, are cells of the immune system that are involved in protecting the body against both infectious disease and foreign entities. White blood cells are genera ...
s, such as
lymphocyte A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), an ...
s, also undergo programmed cell death leading to an abnormally low concentration of lymphocytes in the blood. This contributes to the weakened immune response seen in those infected with EBOV. Endothelial cells may be infected within three days after exposure to the virus. The breakdown of endothelial cells leading to
blood vessel Blood vessels are the tubular structures of a circulatory system that transport blood throughout many Animal, animals’ bodies. Blood vessels transport blood cells, nutrients, and oxygen to most of the Tissue (biology), tissues of a Body (bi ...
injury can be attributed to EBOV
glycoprotein Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...
s. This damage occurs due to the synthesis of Ebola virus
glycoprotein Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...
(GP), which reduces the availability of specific
integrin Integrins are transmembrane receptors that help cell–cell and cell–extracellular matrix (ECM) adhesion. Upon ligand binding, integrins activate signal transduction pathways that mediate cellular signals such as regulation of the cell cycle, o ...
s responsible for cell adhesion to the intercellular structure and causes liver damage, leading to improper clotting. The widespread
bleeding Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethr ...
that occurs in affected people causes swelling and shock due to loss of blood volume. The dysfunctional bleeding and clotting commonly seen in EVD has been attributed to increased activation of the extrinsic pathway of the
coagulation cascade Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of coagulat ...
due to excessive
tissue factor Tissue factor, also called platelet tissue factor or Coagulation factor III, is a protein present in subendothelial tissue and leukocytes which plays a major role in coagulation and, in humans, is encoded by ''F3'' gene. Its role in the blood c ...
production by macrophages and monocytes. After infection, a secreted
glycoprotein Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...
, small soluble glycoprotein (sGP or GP) is synthesised. EBOV replication overwhelms protein synthesis of infected cells and the host immune defences. The GP forms a trimeric complex, which tethers the virus to the endothelial cells. The sGP forms a dimeric protein that interferes with the signalling of
neutrophils Neutrophils are a type of phagocytic white blood cell and part of innate immunity. More specifically, they form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in different ...
, another type of white blood cell. This enables the virus to evade the immune system by inhibiting early steps of neutrophil activation. Furthermore, the virus is capable of hijacking cellular metabolism. Studies have shown that Ebola virus-like particles can reprogram metabolism in both vascular and immune cells.


Immune system evasion

Filoviral infection also interferes with proper functioning of the
innate immune system The innate immune system or nonspecific immune system is one of the two main immunity strategies in vertebrates (the other being the adaptive immune system). The innate immune system is an alternate defense strategy and is the dominant immune s ...
. EBOV proteins blunt the human immune system's response to viral infections by interfering with the cells' ability to produce and respond to interferon proteins such as
interferon-alpha The type-I interferons (IFN) are cytokines which play essential roles in inflammation, immunoregulation, tumor cells recognition, and T-cell responses. In the human genome, a cluster of thirteen functional IFN genes is located at the 9p21.3 cyt ...
,
interferon-beta The type-I interferons (IFN) are cytokines which play essential roles in inflammation, immunoregulation, tumor cells recognition, and T-cell responses. In the human genome, a cluster of thirteen functional IFN genes is located at the 9p21.3 cyt ...
, and
interferon gamma Interferon gamma (IFNG or IFN-γ) is a dimerized soluble cytokine that is the only member of the type II class of interferons. The existence of this interferon, which early in its history was known as immune interferon, was described by E. F. ...
. The VP24 and VP35 structural proteins of EBOV play a key role in this interference. When a cell is infected with EBOV, receptors located in the cell's
cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells ( intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...
(such as
RIG-I RIG-I (retinoic acid-inducible gene I) is a cytosolic pattern recognition receptor (PRR) that can mediate induction of a type-I interferon (IFN1) response. RIG-I is an essential molecule in the innate immune system for recognizing cells that ...
and
MDA5 MDA5 (melanoma differentiation-associated protein 5) is a RIG-I-like receptor dsRNA helicase enzyme that is encoded by the ''IFIH1'' gene in humans. MDA5 is part of the RIG-I-like receptor (RLR) family, which also includes RIG-I and LGP2, and f ...
) or outside of the cytosol (such as Toll-like receptor 3 (TLR3),
TLR7 Toll-like receptor 7, also known as TLR7, is a protein that in humans is encoded by the ''TLR7'' gene. Orthologs are found in mammals and birds. It is a member of the toll-like receptor (TLR) family and detects single stranded RNA. Function T ...
,
TLR8 Toll-like receptor 8 is a protein that in humans is encoded by the ''TLR8'' gene. TLR8 has also been designated as CD288 (cluster of differentiation 288). It is a member of the toll-like receptor (TLR) family. Function TLR8 seems to function d ...
and
TLR9 Toll-like receptor 9 is a protein that in humans is encoded by the ''TLR9'' gene. TLR9 has also been designated as CD289 (cluster of differentiation 289). It is a member of the toll-like receptor (TLR) family. TLR9 is an important receptor expres ...
) recognise infectious molecules associated with the virus. On TLR activation, proteins including
interferon regulatory factor 3 Interferon regulatory factor 3, also known as IRF3, is an interferon regulatory factor. Function IRF3 is a member of the interferon regulatory transcription factor (IRF) family. IRF3 was originally discovered as a homolog of IRF1 and IRF2. ...
and interferon regulatory factor 7 trigger a signalling cascade that leads to the expression of
type 1 interferon The type-I interferons (IFN) are cytokines which play essential roles in inflammation, immunoregulation, tumor cells recognition, and T-cell responses. In the human genome, a cluster of thirteen functional IFN genes is located at the 9p21.3 cy ...
s. The type 1 interferons are then released and bind to the
IFNAR1 Interferon-alpha/beta receptor alpha chain is a protein that in humans is encoded by the ''IFNAR1'' gene. Function The protein encoded by this gene is a type I membrane protein that forms one of the two chains of a receptor for type I interfer ...
and
IFNAR2 Interferon-alpha/beta receptor beta chain is a protein that in humans is encoded by the ''IFNAR2'' gene. Function The protein encoded by this gene is a type I membrane protein that forms one of the two chains of a receptor for interferons a ...
receptors expressed on the surface of a neighbouring cell. Once interferon has bound to its receptors on the neighbouring cell, the signalling proteins
STAT1 Signal transducer and activator of transcription 1 (STAT1) is a transcription factor which in humans is encoded by the ''STAT1'' gene. It is a member of the STAT protein family. Function All STAT molecules are phosphorylated by receptor associ ...
and
STAT2 Signal transducer and activator of transcription 2 is a protein that in humans is encoded by the ''STAT2'' gene. It is a member of the STAT protein family. This protein is critical to the biological response of type I interferons (IFNs). It funct ...
are activated and move to the cell's nucleus. This triggers the expression of interferon-stimulated genes, which code for proteins with antiviral properties. EBOV's V24 protein blocks the production of these antiviral proteins by preventing the STAT1 signalling protein in the neighbouring cell from entering the nucleus. The VP35 protein directly inhibits the production of interferon-beta. By inhibiting these immune responses, EBOV may quickly spread throughout the body.


Diagnosis

When EVD is suspected, travel, work history, and exposure to wildlife are important factors with respect to further diagnostic efforts.


Laboratory testing

Possible non-specific laboratory indicators of EVD include a low platelet count; an initially decreased white blood cell count followed by an increased white blood cell count; elevated levels of the liver enzymes
alanine aminotransferase Alanine aminotransferase (ALT or ALAT), formerly alanine transaminase (ALT), and even earlier referred to as serum glutamate-pyruvate transaminase (GPT) or serum glutamic-pyruvic transaminase (SGPT), is a transaminase enzyme () that was first ch ...
(ALT) and
aspartate aminotransferase Aspartate transaminase (AST) or aspartate aminotransferase, also known as AspAT/ASAT/AAT or (serum) glutamic oxaloacetic transaminase (GOT, SGOT), is a pyridoxal phosphate (PLP)-dependent transaminase enzyme () that was first described by Arthur ...
(AST); and abnormalities in blood clotting often consistent with
disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking Microvessel, small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems ...
(DIC) such as a prolonged
prothrombin time The prothrombin time (PT) – along with its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) – is an assay for evaluating the Coagulation#Extrinsic pathway, extrinsic pathway and Coagulation#Common pathway, ...
,
partial thromboplastin time The partial thromboplastin time (PTT), also known as the activated partial thromboplastin time (aPTT or APTT), is a blood test that characterizes coagulation of the blood. A historical name for this measure is the Kaolin-cephalin clotting time ...
, and
bleeding time Bleeding time is a medical test done to assess the function of a person's platelets. It involves making a patient bleed, then timing how long it takes for them to stop bleeding using a stopwatch or other suitable devices. The term template bleedi ...
. Filovirions such as EBOV may be identified by their unique filamentous shapes in cell cultures examined with
electron microscopy An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing i ...
. The specific diagnosis of EVD is confirmed by isolating the virus, detecting its
RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...
or proteins, or detecting
antibodies An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...
against the virus in a person's blood. Isolating the virus by
cell culture Cell culture or tissue culture is the process by which cell (biology), cells are grown under controlled conditions, generally outside of their natural environment. After cells of interest have been Cell isolation, isolated from living tissue, ...
, detecting the viral RNA by
polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to amplify a very small sample of DNA (or a part of it) sufficiently to enable detailed st ...
(PCR) and detecting proteins by
enzyme-linked immunosorbent assay The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay is a solid-phase type of enzyme immunoassay (EIA) to detect the presence o ...
(ELISA) are methods best used in the early stages of the disease and also for detecting the virus in human remains. Detecting antibodies against the virus is most reliable in the later stages of the disease and in those who recover.
IgM antibodies Immunoglobulin M (IgM) is the largest of several isotypes of antibodies (also known as immunoglobulin) that are produced by vertebrates. IgM is the first antibody to appear in the response to initial exposure to an antigen; causing it to also ...
are detectable two days after symptom onset and
IgG antibodies Immunoglobulin G (IgG) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG ant ...
can be detected six to 18 days after symptom onset. During an outbreak, isolation of the virus with cell culture methods is often not feasible. In field or mobile hospitals, the most common and sensitive diagnostic methods are
real-time PCR A real-time polymerase chain reaction (real-time PCR, or qPCR when used quantitatively) is a laboratory technique of molecular biology based on the polymerase chain reaction (PCR). It monitors the amplification of a targeted DNA molecule duri ...
and ELISA. In 2014, with new mobile testing facilities deployed in parts of Liberia, test results were obtained 3–5 hours after sample submission. In 2015, a rapid antigen test which gives results in 15 minutes was approved for use by WHO. It is able to confirm Ebola in 92% of those affected and rule it out in 85% of those not affected.


Differential diagnosis

Early symptoms of EVD may be similar to those of other diseases common in Africa, including
malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...
and
dengue fever Dengue fever is a mosquito-borne disease caused by dengue virus, prevalent in tropical and subtropical areas. Asymptomatic infections are uncommon, mild cases happen frequently; if symptoms appear, they typically begin 3 to 14 days after i ...
. The symptoms are also similar to those of other viral haemorrhagic fevers such as
Marburg virus disease Marburg (; ) is a university town in the German federal state () of Hesse, capital of the Marburg-Biedenkopf district (). The town area spreads along the valley of the river Lahn and has a population of approximately 76,000. Having been ...
, Crimean–Congo haemorrhagic fever, and
Lassa fever Lassa fever, also known as Lassa hemorrhagic fever, is a type of viral hemorrhagic fever caused by the Lassa virus. Many of those infected by the virus asymptomatic, do not develop symptoms. When symptoms occur they typically include fever, wea ...
. The complete
differential diagnosis In healthcare, a differential diagnosis (DDx) is a method of analysis that distinguishes a particular disease or condition from others that present with similar clinical features. Differential diagnostic procedures are used by clinicians to di ...
is extensive and requires consideration of many other infectious diseases such as
typhoid fever Typhoid fever, also known simply as typhoid, is a disease caused by '' Salmonella enterica'' serotype Typhi bacteria, also called ''Salmonella'' Typhi. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often th ...
,
shigellosis Shigellosis, known historically as dysentery, is an infection of the intestines caused by ''Shigella'' bacteria. Symptoms generally start one to two days after exposure and include diarrhea, fever, abdominal pain, and feeling the need to pass ...
, rickettsial diseases,
cholera Cholera () is an infection of the small intestine by some Strain (biology), strains of the Bacteria, bacterium ''Vibrio cholerae''. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea last ...
,
sepsis Sepsis is a potentially life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage of sepsis is followed by suppression of the immune system. Common signs and s ...
,
borreliosis Lyme disease, also known as Lyme borreliosis, is a tick-borne disease caused by species of ''Borrelia'' bacteria, transmitted by blood-feeding ticks in the genus ''Ixodes''. It is the most common disease spread by ticks in the Northern Hem ...
, EHEC enteritis,
leptospirosis Leptospirosis is a blood infection caused by the bacterium ''Leptospira'' that can infect humans, dogs, rodents and many other wild and domesticated animals. Signs and symptoms can range from none to mild (headaches, Myalgia, muscle pains, a ...
,
scrub typhus Scrub typhus or bush typhus is a form of typhus caused by the intracellular parasite '' Orientia tsutsugamushi'', a Gram-negative α-proteobacterium of family Rickettsiaceae first isolated and identified in 1930 in Japan.plague,
Q fever Q fever or query fever is a disease caused by infection with ''Coxiella burnetii'', a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, including ...
,
candidiasis Candidiasis is a fungal infection due to any species of the genus '' Candida'' (a yeast). When it affects the mouth, in some countries it is commonly called thrush. Signs and symptoms include white patches on the tongue or other areas of the ...
,
histoplasmosis Histoplasmosis is a fungal infection caused by ''Histoplasma capsulatum''. Symptoms of this infection vary greatly, but the disease affects primarily the lungs. Occasionally, other organs are affected; called disseminated histoplasmosis, it can ...
,
trypanosomiasis Trypanosomiasis or trypanosomosis is the name of several diseases in vertebrates caused by parasitic protozoan trypanosomes of the genus ''Trypanosoma''. In humans this includes African trypanosomiasis and Chagas disease. A number of other disea ...
,
visceral In a multicellular organism, an organ is a collection of Tissue (biology), tissues joined in a structural unit to serve a common function. In the biological organization, hierarchy of life, an organ lies between Tissue (biology), tissue and an o ...
leishmaniasis Leishmaniasis is a wide array of clinical manifestations caused by protozoal parasites of the Trypanosomatida genus ''Leishmania''. It is generally spread through the bite of Phlebotominae, phlebotomine Sandfly, sandflies, ''Phlebotomus'' an ...
,
measles Measles (probably from Middle Dutch or Middle High German ''masel(e)'', meaning "blemish, blood blister") is a highly contagious, Vaccine-preventable diseases, vaccine-preventable infectious disease caused by Measles morbillivirus, measles v ...
, and viral hepatitis among others. Non-infectious diseases that may result in symptoms similar to those of EVD include
acute promyelocytic leukaemia Acute promyelocytic leukemia (APML, APL) is a subtype of acute myeloid leukemia (AML), a cancer of the white blood cells. In APL, there is an abnormal accumulation of immature granulocytes called promyelocytes. The disease is characterized by ...
,
haemolytic uraemic syndrome Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo ...
, snake envenomation,
clotting factor Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of coagulation ...
deficiencies/platelet disorders,
thrombotic thrombocytopenic purpura Thrombotic thrombocytopenic purpura (TTP) is a blood disorder that results in thrombi, blood clots forming in small blood vessels throughout the body. This results in a thrombocytopenia, low platelet count, hemolytic anemia, low red blood cells d ...
,
hereditary haemorrhagic telangiectasia Hereditary hemorrhagic telangiectasia (HHT), also known as Osler–Weber–Rendu disease and Osler–Weber–Rendu syndrome, is a rare autosomal dominant genetic disorder that leads to abnormal blood vessel formation in the Human skin, skin, muco ...
,
Kawasaki disease Kawasaki disease (also known as mucocutaneous lymph node syndrome) is a syndrome of unknown cause that results in a fever and mainly affects children under 5 years of age. It is a form of vasculitis, in which medium-sized blood vessels become in ...
, and
warfarin Warfarin, sold under the brand name Coumadin among others. It is used as an anticoagulant, anticoagulant medication. It is commonly used to prevent deep vein thrombosis and pulmonary embolism, and to protect against stroke in people who ha ...
poisoning.


Prevention


Vaccines

An
Ebola vaccine Ebola vaccines are vaccines either approved or in development to prevent Ebola. As of 2022, there are only vaccines against the Zaire ebolavirus. The first vaccine to be approved in the United States was rVSV-ZEBOV in December 2019. It had ...
,
rVSV-ZEBOV Recombinant vesicular stomatitis virus–Zaire Ebola virus (rVSV-ZEBOV), also known as Ebola Zaire vaccine live and sold under the brand name Ervebo, is an Ebola vaccine for adults that prevents Ebola caused by the Zaire ebolavirus. When used ...
, was approved in the United States in December 2019. It appears to be fully effective ten days after being given. It was studied in Guinea between 2014 and 2016. More than 100,000 people have been vaccinated against Ebola . The WHO reported that approximately 345,000 people were given the vaccine during the
Kivu Ebola epidemic The Kivu Ebola epidemic was an outbreak of Ebola virus disease (EVD) mainly in eastern Democratic Republic of the Congo (DRC), and in other parts of Central Africa, from 2018 to 2020. Between 1 August 2018 and 25 June 2020 it resulted in 3,470 ...
from 2018 to 2020.


Infection control

Community awareness of the benefits on survival chances of admitting cases early is important for the infected and infection control


Caregivers

People who care for those infected with Ebola should wear protective clothing including masks, gloves, gowns and goggles. The U.S.
Centers for Disease Control The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency under the Department of Health and Human Services (HHS), and is headquartered in Atlanta, ...
(CDC) recommend that the protective gear leaves no skin exposed. These measures are also recommended for those who may handle objects contaminated by an infected person's body fluids. In 2014, the CDC began recommending that medical personnel receive training on the proper suit-up and removal of
personal protective equipment Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, elect ...
(PPE); in addition, a designated person, appropriately trained in biosafety, should be watching each step of these procedures to ensure they are done correctly. In Sierra Leone, the typical training period for the use of such safety equipment lasts approximately 12 days. In 2022 in Uganda, lighter personal protection equipment has become available as well as possibilities to monitor and communicate with patients from windows in the treatment tents until it is necessary to enter if e.g. a patient's oxygen levels drop.


Patients and household members

The infected person should be in barrier-isolation from other people. All equipment, medical waste, patient waste and surfaces that may have come into contact with body fluids need to be disinfected. During the 2014 outbreak, kits were put together to help families treat Ebola disease in their homes, which included protective clothing as well as
chlorine powder Chlorine is a chemical element; it has symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a ...
and other cleaning supplies. Education of caregivers in these techniques, and providing such barrier-separation supplies has been a priority of
Doctors Without Borders Doctor, Doctors, The Doctor or The Doctors may refer to: Titles and occupations * Physician, a medical practitioner * Doctor (title), an academic title for the holder of a doctoral-level degree ** Doctorate ** List of doctoral degrees awarded ...
.


Disinfection

Ebolaviruses can be eliminated with heat (heating for 30 to 60 minutes at 60 Â°C or boiling for five minutes). To
disinfect A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant endospore, bacterial spores; it is less effect ...
surfaces, some lipid solvents such as some alcohol-based products, detergents, sodium hypochlorite (bleach) or
calcium hypochlorite Calcium hypochlorite is an inorganic compound with chemical formula , also written as . It is a white solid, although commercial samples appear yellow. It strongly smells of chlorine, owing to its slow decomposition in moist air. This compound is ...
(bleaching powder), and other suitable disinfectants may be used at appropriate concentrations.


General population

Education of the general public about the risk factors for Ebola infection and of the protective measures individuals may take to prevent infection is recommended by the
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
. These measures include avoiding direct contact with infected people and regular
hand washing Hand washing (or handwashing), also known as hand hygiene, is the act of cleaning one's hands with soap, soap or handwash and water to remove viruses, bacteria, microorganisms, dirt, grease, and other harmful or unwanted substances stuck to th ...
using soap and water.


Bushmeat

Bushmeat Bushmeat is meat from wildlife species that are Hunting, hunted for human consumption. Bushmeat represents a primary source of animal protein and a cash-earning commodity in poor and rural communities of humid tropical forest regions of the worl ...
, an important source of protein in the diet of some Africans, should be handled and prepared with appropriate protective clothing and thoroughly cooked before consumption. Some research suggests that an outbreak of Ebola disease in the wild animals used for consumption may result in a corresponding human outbreak. Since 2003, such animal outbreaks have been monitored to predict and prevent Ebola outbreaks in humans.


Corpses, burial

If a person with Ebola disease dies, direct contact with the body should be avoided. Certain burial rituals, which may have included making various direct contacts with a dead body, require reformulation so that they consistently maintain a proper protective barrier between the dead body and the living. Social anthropologists may help find alternatives to traditional rules for burials.


Transport, travel, contact

Transportation crews are instructed to follow a certain isolation procedure, should anyone exhibit symptoms resembling EVD. , the WHO does not consider travel bans to be useful in decreasing spread of the disease. In October 2014, the CDC defined four risk levels used to determine the level of 21-day monitoring for symptoms and restrictions on public activities. In the United States, the CDC recommends that restrictions on public activity, including travel restrictions, are not required for the following defined risk levels: * having been in a country with widespread Ebola disease transmission and having no known exposure (low risk); or having been in that country more than 21 days ago (no risk) * encounter with a person showing symptoms; but not within three feet of the person with Ebola without wearing PPE; and no direct contact with body fluids * having had brief skin contact with a person showing symptoms of Ebola disease when the person was believed to be not very contagious (low risk) * in countries without widespread Ebola disease transmission: direct contact with a person showing symptoms of the disease while wearing PPE (low risk) * contact with a person with Ebola disease before the person was showing symptoms (no risk). The CDC recommends monitoring for the symptoms of Ebola disease for those both at "low risk" and at higher risk.


Laboratory

In laboratories where diagnostic testing is carried out, biosafety level 4-equivalent containment is required. Laboratory researchers must be properly trained in BSL-4 practices and wear proper PPE.


Isolation

Isolation refers to separating those who are sick from those who are not.
Quarantine A quarantine is a restriction on the movement of people, animals, and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have bee ...
refers to separating those who may have been exposed to a disease until they either show signs of the disease or are no longer at risk. Quarantine, also known as enforced isolation, is usually effective in decreasing spread. Governments often quarantine areas where the disease is occurring or individuals who may transmit the disease outside of an initial area. In the United States, the law allows quarantine of those infected with ebolaviruses.


Contact tracing

Contact tracing In public health, contact tracing is the process of identifying people who may have been exposed to an infected person ("contacts") and subsequent collection of further data to assess transmission. By tracing the contacts of infected individua ...
is considered important to contain an outbreak. It involves finding everyone who had close contact with infected individuals and monitoring them for signs of illness for 21 days. If any of these contacts comes down with the disease, they should be isolated, tested and treated. Then the process is repeated, tracing the contacts' contacts.


Management

two treatments (
atoltivimab/maftivimab/odesivimab Atoltivimab/maftivimab/odesivimab, sold under the brand name INMAZEB, is a fixed-dose combination of three monoclonal antibodies for the treatment of ''Zaire ebolavirus'' (Ebola virus). It was developed by Regeneron Pharmaceuticals and contain ...
and ansuvimab) are associated with improved outcomes. The U.S.
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
(FDA) advises people to be careful of advertisements making unverified or fraudulent claims of benefits supposedly gained from various anti-Ebola products. In October 2020, the U.S.
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
(FDA) approved atoltivimab/maftivimab/odesivimab with an indication for the treatment of infection caused by ''Zaire ebolavirus''.


Standard support

Treatment is primarily supportive in nature. Early supportive care with rehydration and symptomatic treatment improves survival. Rehydration may be via the
oral The word oral may refer to: Relating to the mouth * Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid **Oral administration of medicines ** Oral examination (also known as an oral exam or ora ...
or
intravenous Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...
route. These measures may include
pain management Pain management is an aspect of medicine and health care involving relief of pain (pain relief, analgesia, pain control) in various dimensions, from acute (medicine), acute and simple to chronic condition, chronic and challenging. Most physici ...
, and treatment for
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat. Over 30 d ...
,
fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...
, and
anxiety Anxiety is an emotion characterised by an unpleasant state of inner wikt:turmoil, turmoil and includes feelings of dread over Anticipation, anticipated events. Anxiety is different from fear in that fear is defined as the emotional response ...
. The
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
(WHO) recommends avoiding
aspirin Aspirin () is the genericized trademark for acetylsalicylic acid (ASA), a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and inflammation, and as an antithrombotic. Specific inflammatory conditions that aspirin is ...
or
ibuprofen Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that is used to relieve pain, fever, and inflammation. This includes dysmenorrhea, painful menstrual periods, migraines, and rheumatoid arthritis. It can be taken oral administration, ...
for pain management, due to the risk of bleeding associated with these medications. Blood products such as
packed red blood cells Red blood cell concentrates, also known as red cell concentrates or packed red blood cells, are red blood cells that have been separated for blood transfusion. A red blood cell concentrate typically has a haematocrit of 0.50 – 0.70 L/L and ...
,
platelet Platelets or thrombocytes () are a part of blood whose function (along with the coagulation#Coagulation factors, coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a thrombus, blood clot. Platelets have no ...
s, or
fresh frozen plasma Fresh frozen plasma (FFP) is a blood product made from the liquid portion of whole blood. It is used to treat conditions in which there are low blood clotting factors (INR > 1.5) or low levels of other blood proteins. It may also be used as the r ...
may also be used. Other regulators of coagulation have also been tried including
heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Heparin is a blood anticoagulant that increases the activity of antithrombin. It is used in the treatment of myocardial infarction, ...
in an effort to prevent
disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking Microvessel, small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems ...
and
clotting factors Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of coagulatio ...
to decrease bleeding.
Antimalarial medication Antimalarial medications or simply antimalarials are a type of antiparasitic chemical agent, often natural product, naturally derived, that can be used to treat or to prevent malaria, in the latter case, most often aiming at two susceptible target ...
s and
antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...
are often used before the diagnosis is confirmed, though there is no evidence to suggest such treatment helps. Several experimental treatments are being studied. Where hospital care is not possible, the WHO's guidelines for home care have been relatively successful. Recommendations include using towels soaked in a bleach solution when moving infected people or bodies and also applying bleach on stains. It is also recommended that the caregivers wash hands with bleach solutions and cover their mouth and nose with a cloth.


Intensive care

Intensive care Intensive care medicine, usually called critical care medicine, is a medical specialty that deals with seriously or critically ill patients who have, are at risk of, or are recovering from conditions that may be life-threatening. It includes p ...
is often used in the developed world. This may include maintaining blood volume and electrolytes (salts) balance as well as treating any bacterial infections that may develop.
Dialysis Dialysis may refer to: * Dialysis (chemistry), a process of separating molecules in solution **Electrodialysis, used to transport salt ions from one solution to another through an ion-exchange membrane under the influence of an applied electric po ...
may be needed for
kidney failure Kidney failure, also known as renal failure or end-stage renal disease (ESRD), is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney fa ...
, and
extracorporeal membrane oxygenation Extracorporeal membrane oxygenation (ECMO) is a form of extracorporeal life support, providing prolonged cardiac and respiratory system, respiratory support to people whose human heart, heart and human lung, lungs are unable to provide an adequa ...
may be used for lung dysfunction.


Prognosis

EVD has a risk of death in those infected of between 25% and 90%. , the average risk of death among those infected is 50%. The highest risk of death was 90% in the 2002–2003
Republic of the Congo The Republic of the Congo, also known as Congo-Brazzaville, the Congo Republic or simply the Congo (the last ambiguously also referring to the neighbouring Democratic Republic of the Congo), is a country located on the western coast of Central ...
outbreak. Early admission significantly increases survival rates Death, if it occurs, follows typically six to sixteen days after symptoms appear and is often due to low blood pressure from fluid loss. Early supportive care to prevent dehydration may reduce the risk of death.


Post-Ebola virus syndrome

If an infected person survives, recovery may be quick and complete. However, a large portion of survivors develop post-Ebola virus syndrome after the acute phase of the infection. Prolonged cases are often complicated by the occurrence of long-term problems, such as inflammation of the testicles, joint pains, fatigue, hearing loss, mood and sleep disturbances,
muscular pain Myalgia or muscle pain is a painful sensation evolving from muscle tissue. It is a symptom of many diseases. The most common cause of acute (medicine), acute myalgia is the overuse of a muscle or Muscle group, group of muscles; another likely c ...
, abdominal pain, menstrual abnormalities,
miscarriage Miscarriage, also known in medical terms as a spontaneous abortion, is an end to pregnancy resulting in the loss and expulsion of an embryo or fetus from the womb before it can fetal viability, survive independently. Miscarriage before 6 weeks ...
s,
skin peeling Desquamation, or peeling skin, is the shedding of dead cells from the outermost layer of skin. The term is . Physiologic desquamation Keratinocytes are the predominant cells of the epidermis, the outermost layer of the skin. Living keratin ...
, or
hair loss Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarring ...
. Inflammation and swelling of the uveal layer of the eye is the most common eye complication in survivors of Ebola virus disease. Eye symptoms, such as
light sensitivity Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicity ...
, excess tearing, and
vision loss Visual or vision impairment (VI or VIP) is the partial or total inability of visual perception. In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficul ...
have been described. Ebola can stay in some body parts like the eyes, breasts, and testicles after infection. Sexual transmission after recovery has been suspected. If sexual transmission occurs following recovery it is believed to be a rare event. One case of a condition similar to
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasion ...
has been reported many months after recovery, .


Epidemiology

The disease typically occurs in outbreaks in tropical regions of
Sub-Saharan Africa Sub-Saharan Africa is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern Africa, and West Africa. Geopolitically, in addition to the list of sovereign states and ...
. From 1976 (when it was first identified) through 2013, the WHO reported 2,387 confirmed cases with 1,590 overall fatalities. The largest outbreak to date was the
Ebola virus epidemic in West Africa The 2013–2016 epidemic of Ebola virus disease, centered in West Africa, was the most widespread outbreak of the disease in history. It caused major loss of life and socioeconomic disruption in the region, mainly in Guinea, Liberia and S ...
, which caused a large number of deaths in
Guinea Guinea, officially the Republic of Guinea, is a coastal country in West Africa. It borders the Atlantic Ocean to the west, Guinea-Bissau to the northwest, Senegal to the north, Mali to the northeast, Côte d'Ivoire to the southeast, and Sier ...
,
Sierra Leone Sierra Leone, officially the Republic of Sierra Leone, is a country on the southwest coast of West Africa. It is bordered to the southeast by Liberia and by Guinea to the north. Sierra Leone's land area is . It has a tropical climate and envi ...
, and
Liberia Liberia, officially the Republic of Liberia, is a country on the West African coast. It is bordered by Sierra Leone to Liberia–Sierra Leone border, its northwest, Guinea to Guinea–Liberia border, its north, Ivory Coast to Ivory Coast–Lib ...
.


1976


Sudan

The first known outbreak of EVD was identified only after the fact. It occurred between June and November 1976, in
Nzara, South Sudan Nzara is a town in Western Equatoria State. It lies to the northwest of Yambio by road, and is 25 km (15m) from the border with the DR Congo. Nzara was industrial center of the Azande Scheme also known as, Equatoria Project Scheme during ...
(then part of
Sudan Sudan, officially the Republic of the Sudan, is a country in Northeast Africa. It borders the Central African Republic to the southwest, Chad to the west, Libya to the northwest, Egypt to the north, the Red Sea to the east, Eritrea and Ethiopi ...
), and was caused by Sudan virus (SUDV). The Sudan outbreak infected 284 people and killed 151. The first identifiable case in Sudan occurred on 27 June in a storekeeper in a cotton factory in Nzara, who was hospitalised on 30 June and died on 6 July. Although the WHO medical staff involved in the Sudan outbreak knew that they were dealing with a heretofore unknown disease, the actual "positive identification" process and the naming of the virus did not occur until some months later in
Zaire Zaire, officially the Republic of Zaire, was the name of the Democratic Republic of the Congo from 1971 to 18 May 1997. Located in Central Africa, it was, by area, the third-largest country in Africa after Sudan and Algeria, and the 11th-la ...
.


Zaire

On 26 August 1976, the second outbreak of EVD began in
Yambuku Yambuku is a small village in Mongala, Mongala Province in northern Democratic Republic of the Congo. It was the center of the first documented outbreak of Ebola, Ebola virus disease, in 1976, with the World Health Organization identifying a man fr ...
, a small rural village in
Mongala District Mongala District (, ) was a district of the Belgian Congo and the Democratic Republic of the Congo. It went through various changes in extent. It covered roughly the same area as the present Mongala province and most of Nord-Ubangi province. Loca ...
in northern
Zaire Zaire, officially the Republic of Zaire, was the name of the Democratic Republic of the Congo from 1971 to 18 May 1997. Located in Central Africa, it was, by area, the third-largest country in Africa after Sudan and Algeria, and the 11th-la ...
(now known as the
Democratic Republic of the Congo The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...
). This outbreak was caused by EBOV, formerly designated ''Zaire ebolavirus'', a different member of the
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''Ebolavirus'' than in the first Sudan outbreak. The first person infected with the disease was the village school's headmaster Mabalo Lokela, who began displaying symptoms on 26 August 1976. Lokela had returned from a trip to Northern Zaire near the border of the
Central African Republic The Central African Republic (CAR) is a landlocked country in Central Africa. It is bordered by Chad to Central African Republic–Chad border, the north, Sudan to Central African Republic–Sudan border, the northeast, South Sudan to Central ...
, after visiting the
Ebola River The Ebola River ( or ), also commonly known by its Ngbandi name Legbala, is the headstream of the Mongala River, a tributary of the Congo River, in northern Democratic Republic of the Congo. It is roughly in length. The name ''Ebola'' is a Fre ...
between 12 and 22 August. He was originally believed to have
malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...
and was given
quinine Quinine is a medication used to treat malaria and babesiosis. This includes the treatment of malaria due to ''Plasmodium falciparum'' that is resistant to chloroquine when artesunate is not available. While sometimes used for nocturnal leg ...
. However, his symptoms continued to worsen, and he was admitted to Yambuku Mission Hospital on 5 September. Lokela died on 8 September 14 days after he began displaying symptoms. Soon after Lokela's death, others who had been in contact with him also died, and people in Yambuku began to panic. The country's Minister of Health and Zaire President
Mobutu Sese Seko Mobutu Sese Seko Kuku Ngbendu wa za Banga ( ; born Joseph-Désiré Mobutu; 14 October 1930 – 7 September 1997), often shortened to Mobutu Sese Seko or Mobutu and also known by his initials MSS, was a Congolese politician and military officer ...
declared the entire region, including Yambuku and the country's capital,
Kinshasa Kinshasa (; ; ), formerly named Léopoldville from 1881–1966 (), is the Capital city, capital and Cities of the Democratic Republic of the Congo, largest city of the Democratic Republic of the Congo. Kinshasa is one of the world's fastest-grow ...
, a quarantine zone. No-one was permitted to enter or leave the area, and roads, waterways, and airfields were placed under
martial law Martial law is the replacement of civilian government by military rule and the suspension of civilian legal processes for military powers. Martial law can continue for a specified amount of time, or indefinitely, and standard civil liberties ...
. Schools, businesses and social organisations were closed. The initial response was led by Congolese doctors, including
Jean-Jacques Muyembe-Tamfum Jean-Jacques Muyembe is a Congolese microbiologist. He is the general director of the Democratic Republic of the Congo Institut National pour la Recherche Biomedicale (''INRB''). He was part of team at the Yambuku Catholic Mission Hospital that i ...
, one of the discoverers of Ebola. Muyembe took a blood sample from a Belgian nun; this sample would eventually be used by
Peter Piot Sir Peter Karel, Baron Piot (born 17 February 1949) is a Belgian-British microbiologist known for his research into Ebola and AIDS. After helping discover the Ebola virus in 1976 and leading efforts to contain the first-ever recorded Ebola epide ...
to identify the previously unknown Ebola virus. Muyembe was also the first scientist to come into direct contact with the disease and survive. Researchers from the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the National public health institutes, national public health agency of the United States. It is a Federal agencies of the United States, United States federal agency under the United S ...
(CDC), including Piot, co-discoverer of Ebola, later arrived to assess the effects of the outbreak, observing that "the whole region was in panic." Piot concluded that Belgian nuns had inadvertently started the epidemic by giving unnecessary vitamin injections to pregnant women without sterilizing the syringes and needles. The outbreak lasted 26 days and the quarantine lasted two weeks. Researchers speculated that the disease disappeared due to the precautions taken by locals, the quarantine of the area, and discontinuing of the injections. During this outbreak, Ngoy Mushola recorded the first clinical description of EVD in
Yambuku Yambuku is a small village in Mongala, Mongala Province in northern Democratic Republic of the Congo. It was the center of the first documented outbreak of Ebola, Ebola virus disease, in 1976, with the World Health Organization identifying a man fr ...
, where he wrote the following in his daily log: "The illness is characterised with a high temperature of about , haematemesis, diarrhoea with blood, retrosternal abdominal pain, prostration with 'heavy' articulations, and rapid evolution death after a mean of three days." The virus responsible for the initial outbreak, first thought to be the
Marburg virus Marburg virus (MARV) is a hemorrhagic fever virus of the '' Filoviridae'' family of viruses and a member of the species '' Marburg marburgvirus'', genus '' Marburgvirus''. It causes Marburg virus disease in primates, a form of viral hemorrhag ...
, was later identified as a new type of virus related to the genus ''
Marburgvirus The genus ''Marburgvirus'' is the taxonomic home of ''Marburg marburgvirus'', whose members are the two known marburgviruses, Marburg virus (MARV) and Ravn virus (RAVV). Both viruses cause Marburg virus disease in humans and nonhuman primat ...
''. Virus strain samples isolated from both outbreaks were named "Ebola virus" after the
Ebola River The Ebola River ( or ), also commonly known by its Ngbandi name Legbala, is the headstream of the Mongala River, a tributary of the Congo River, in northern Democratic Republic of the Congo. It is roughly in length. The name ''Ebola'' is a Fre ...
, near the first-identified viral outbreak site in Zaire. Reports conflict about who initially coined the name: either Karl Johnson of the American CDC team or Belgian researchers. Subsequently, a number of other cases were reported, almost all centred on the Yambuku mission hospital or close contacts of another case. In all, 318 cases and 280 deaths (an 88% fatality rate) occurred in Zaire. Although the two outbreaks were at first believed connected, scientists later realised that they were caused by two distinct ebolaviruses, SUDV and EBOV.


1995–2014

The second major outbreak occurred in Zaire (now the
Democratic Republic of the Congo The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...
, DRC), in 1995, affecting 315 and killing 254. In 2000,
Uganda Uganda, officially the Republic of Uganda, is a landlocked country in East Africa. It is bordered to the east by Kenya, to the north by South Sudan, to the west by the Democratic Republic of the Congo, to the south-west by Rwanda, and to the ...
had an outbreak infecting 425 and killing 224; in this case, the Sudan virus was found to be the Ebola species responsible for the outbreak. In 2003, an outbreak in the DRC infected 143 and killed 128, a 90% death rate, the highest of a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''Ebolavirus'' outbreak to date. In 2004, a Russian scientist died from Ebola after sticking herself with an infected needle. Between April and August 2007, a fever epidemic in a four-village region of the DRC was confirmed in September to have been cases of Ebola. Many people who attended the recent funeral of a local village chief died. The 2007 outbreak eventually infected 264 individuals and killed 187. On 30 November 2007, the Uganda Ministry of Health confirmed an outbreak of Ebola in the
Bundibugyo District Bundibugyo District is a Districts of Uganda, district in the Western Region, Uganda, Western Region of Uganda, bordering the Democratic Republic of the Congo (DRC). The town of Bundibugyo is where both the district headquarters and the Bwamba Kin ...
in Western Uganda. After confirming samples tested by the United States National Reference Laboratories and the Centers for Disease Control, the World Health Organization (WHO) confirmed the presence of a new species of
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''Ebolavirus'', which was tentatively named Bundibugyo. The WHO reported 149 cases of this new strain and 37 of those led to deaths. The WHO confirmed two small outbreaks in Uganda in 2012, both caused by the Sudan variant. The first outbreak affected seven people, killing four, and the second affected 24, killing 17. On 17 August 2012, the Ministry of Health of the DRC reported an outbreak of the Ebola-Bundibugyo variant in the eastern region. Other than its discovery in 2007, this was the only time that this variant has been identified as responsible for an outbreak. The WHO revealed that the virus had sickened 57 people and killed 29. The probable cause of the outbreak was tainted
bush meat A bush or shrub is a small or medium woody plant. Bush or Bushes may also refer to: People * Bush (surname), including any of several people with that name ** Bush family, a prominent American family that includes: ***Prescott Bush (1895-1972), ...
hunted by local villagers around the towns of
Isiro Isiro () is the capital of Haut-Uele Province in the northeastern part of the Democratic Republic of the Congo. It lies between the Tropical rainforest, equatorial forest and the savannah and its main resource is coffee. Isiro's population is est ...
and Viadana. In 2014, an outbreak occurred in the DRC. Genome-sequencing showed that this outbreak was not related to the 2014–15 West Africa Ebola virus outbreak, but was the same
EBOV ''Orthoebolavirus zairense'' or Zaire ebolavirus, more commonly known as Ebola virus (; EBOV), is one of six known species within the genus ''Ebolavirus''. Four of the six known ebolaviruses, including EBOV, cause a severe and often fatal vira ...
species, the Zaire species. It began in August 2014, and was declared over in November with 66 cases and 49 deaths. This was the 7th outbreak in the DRC, three of which occurred during the period when the country was known as
Zaire Zaire, officially the Republic of Zaire, was the name of the Democratic Republic of the Congo from 1971 to 18 May 1997. Located in Central Africa, it was, by area, the third-largest country in Africa after Sudan and Algeria, and the 11th-la ...
.


2013–2016 West Africa

In March 2014, the
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
(WHO) reported a major Ebola outbreak in
Guinea Guinea, officially the Republic of Guinea, is a coastal country in West Africa. It borders the Atlantic Ocean to the west, Guinea-Bissau to the northwest, Senegal to the north, Mali to the northeast, Côte d'Ivoire to the southeast, and Sier ...
, a West African nation. Researchers traced the outbreak to a one-year-old child who died in December 2013. The disease rapidly spread to the neighbouring countries of
Liberia Liberia, officially the Republic of Liberia, is a country on the West African coast. It is bordered by Sierra Leone to Liberia–Sierra Leone border, its northwest, Guinea to Guinea–Liberia border, its north, Ivory Coast to Ivory Coast–Lib ...
and
Sierra Leone Sierra Leone, officially the Republic of Sierra Leone, is a country on the southwest coast of West Africa. It is bordered to the southeast by Liberia and by Guinea to the north. Sierra Leone's land area is . It has a tropical climate and envi ...
. It was the largest Ebola outbreak ever documented, and the first recorded in the region. On 8 August 2014, the WHO declared the epidemic an international public health emergency. Urging the world to offer aid to the affected regions, its Director-General said, "Countries affected to date simply do not have the capacity to manage an outbreak of this size and complexity on their own. I urge the international community to provide this support on the most urgent basis possible." By mid-August 2014,
Doctors Without Borders Doctor, Doctors, The Doctor or The Doctors may refer to: Titles and occupations * Physician, a medical practitioner * Doctor (title), an academic title for the holder of a doctoral-level degree ** Doctorate ** List of doctoral degrees awarded ...
reported the situation in Liberia's capital,
Monrovia Monrovia () is the administrative capital city, capital and largest city of Liberia. Founded in 1822, it is located on Cape Mesurado on the Atlantic Ocean, Atlantic coast and as of the 2022 census had 1,761,032 residents, home to 33.5% of Liber ...
, was "catastrophic" and "deteriorating daily". They reported that fears of Ebola among staff members and patients had shut down much of the city's health system, leaving many people without medical treatment for other conditions. In a 26 September statement, WHO said, "The Ebola epidemic ravaging parts of West Africa is the most severe acute public health emergency seen in modern times. Never before in recorded history has a biosafety level four pathogen infected so many people so quickly, over such a broad geographical area, for so long." Intense contact tracing and strict isolation largely prevented further spread of the disease in the countries that had imported cases. , suspected cases and deaths were reported; however, the WHO said that these numbers may be underestimated. Because they work closely with the body fluids of infected patients, healthcare workers were especially vulnerable to infection; in August 2014, the WHO reported that 10% of the dead were healthcare workers. In September 2014, it was estimated that the countries' capacity for treating Ebola patients was insufficient by the equivalent of 2,122 beds; by December there were a sufficient number of beds to treat and isolate all reported Ebola cases, although the uneven distribution of cases was causing serious shortfalls in some areas. On 28 January 2015, the WHO reported that for the first time since the week ending 29 June 2014, there had been fewer than 100 new confirmed cases reported in a week in the three most-affected countries. The response to the epidemic then moved to a second phase, as the focus shifted from slowing transmission to ending the epidemic. On 8 April 2015, the WHO reported only 30 confirmed cases, the lowest weekly total since the third week of May 2014. On 29 December 2015, 42 days after the last person tested negative for a second time, Guinea was declared free of Ebola transmission. At that time, a 90-day period of heightened surveillance was announced by that agency. "This is the first time that all three countries – Guinea, Liberia and Sierra Leone – have stopped the original chains of transmission ...", the organisation stated in a news release. A new case was detected in Sierra Leone on 14 January 2016. However, the outbreak was declared no longer an emergency on 29 March 2016.


2014 spread outside West Africa

On 19 September, Eric Duncan flew from his native Liberia to Texas; five days later he began showing symptoms and visited a hospital but was sent home. His condition worsened and he returned to the hospital on 28 September, where he died on 8 October. Health officials confirmed a diagnosis of Ebola on 30 September – the first case in the United States. In early October, Teresa Romero, a 44-year-old Spanish nurse, contracted Ebola after caring for a priest who had been repatriated from West Africa. This was the first transmission of the virus to occur outside Africa. Romero tested negative for the disease on 20 October, suggesting that she may have recovered from Ebola infection. On 12 October, the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the National public health institutes, national public health agency of the United States. It is a Federal agencies of the United States, United States federal agency under the United S ...
(CDC) confirmed that a nurse in Texas, Nina Pham, who had treated Duncan tested positive for the Ebola virus, the first known case of transmission in the United States. On 15 October, a second Texas health-care worker who had treated Duncan was confirmed to have the virus. Both of these people recovered. An unrelated case involved a doctor in New York City, who returned to the United States from Guinea after working with
Médecins Sans Frontières (MSF; pronounced ), known in some English-speaking settings as Doctors Without Borders, is a charity that provides humanitarian medical care. It is a non-governmental organisation (NGO) of French origin known for its projects in conflict zo ...
and tested positive for Ebola on 23 October. The person recovered and was discharged from
Bellevue Hospital Bellevue Hospital (officially NYC Health + Hospitals/Bellevue and formerly known as Bellevue Hospital Center) is a hospital in New York City and the oldest public hospital in the United States. One of the largest hospitals in the United States ...
on 11 November. On 24 December 2014, a laboratory in
Atlanta Atlanta ( ) is the List of capitals in the United States, capital and List of municipalities in Georgia (U.S. state), most populous city in the U.S. state of Georgia (U.S. state), Georgia. It is the county seat, seat of Fulton County, Georg ...
, Georgia reported that a technician had been exposed to Ebola. On 29 December 2014,
Pauline Cafferkey Pauline Cafferkey is a Scottish nurse and aid worker who contracted Ebola virus disease in 2014 while working in Sierra Leone as part of the medical aid effort during the West African Ebola virus epidemic. She survived the illness. Initial admi ...
, a British nurse who had just returned to
Glasgow Glasgow is the Cities of Scotland, most populous city in Scotland, located on the banks of the River Clyde in Strathclyde, west central Scotland. It is the List of cities in the United Kingdom, third-most-populous city in the United Kingdom ...
from Sierra Leone, was diagnosed with Ebola at Glasgow's
Gartnavel General Hospital Gartnavel General Hospital is a teaching hospital in the West End of Glasgow, Scotland. The hospital is located next to the Great Western Road, between Hyndland, Anniesland and Kelvindale. Hyndland railway station is adjacent to the hospital. ...
. After initial treatment in Glasgow, she was transferred by air to
RAF Northolt Royal Air Force Northolt or more simply RAF Northolt is a Royal Air Force List of Royal Air Force stations, station in South Ruislip, from Uxbridge in the London Borough of Hillingdon, western Greater London, England, approximately north of ...
, then to the specialist high-level isolation unit at the
Royal Free Hospital The Royal Free Hospital (also known as the Royal Free) is a major teaching hospital in the Hampstead area of the London Borough of Camden. The hospital is part of the Royal Free London NHS Foundation Trust, which also runs services at Barnet Ho ...
in
London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
for longer-term treatment.


2017 Democratic Republic of the Congo

On 11 May 2017, the DRC Ministry of Public Health notified the WHO about an outbreak of Ebola. Four people died, and four people survived; five of these eight cases were laboratory-confirmed. A total of 583 contacts were monitored. On 2 July 2017, the WHO declared the end of the outbreak.


2018 Équateur province

On 14 May 2018, the World Health Organization reported that "the Democratic Republic of Congo reported 39 suspected, probable or confirmed cases of Ebola between 4 April and 13 May, including 19 deaths." Some 393 people identified as contacts of Ebola patients were being followed up. The outbreak centred on the
Bikoro Bikoro is a market town in Équateur Province in the Democratic Republic of the Congo, lying on Lake Tumba, south of Mbandaka. It is the administrative center of Bikoro Territory. In 2012, the estimated population was 7,426. Bikoro was the ...
, Iboko, and Wangata areas in Equateur province, including in the large city of
Mbandaka Mbandaka (, formerly known as Coquilhatville in French, or Coquilhatstad in Dutch) is a city in the Democratic Republic of Congo located near the confluence of the Congo and Ruki rivers. It is the capital of Équateur Province. The city was f ...
. The DRC Ministry of Public Health approved the use of an experimental vaccine. On 13 May 2018, WHO Director-General
Tedros Adhanom Ghebreyesus Tedros Adhanom Ghebreyesus (, sometimes spelled ; born 3 March 1965) is an Ethiopian public health official, researcher, diplomat, and the DGWHO, Director-General of the World Health Organization since 2017. He is the first African to become W ...
visited Bikoro. Reports emerged that maps of the area were inaccurate, not so much hampering medical providers as
epidemiologist Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population, and application of this knowledge to prevent diseases. It is a cornerstone ...
s and officials trying to assess the outbreak and containment efforts. The 2018 outbreak in the DRC was declared over on 24 July 2018.


2018–2020 Kivu

On 1 August 2018, the world's 10th Ebola outbreak was declared in
North Kivu North Kivu () is a Provinces of the Democratic Republic of the Congo, province bordering Lake Kivu in the eastern Democratic Republic of the Congo. The capital city is Goma. Spanning approximately 59,483 square kilometers with a population esti ...
province of the Democratic Republic of the Congo. It was the first Ebola outbreak in a military conflict zone, with thousands of refugees in the area. By November 2018, nearly 200 Congolese had died of Ebola, about half of them from the city of Beni, where armed groups are fighting over the region's mineral wealth, impeding medical relief efforts. By March 2019, this became the second largest Ebola outbreak ever recorded, with more than 1,000 cases and insecurity continuing to be the major resistance to providing an adequate response. , the WHO reported 2025 confirmed and probable cases with 1357 deaths. In June 2019, two people died of Ebola in neighbouring
Uganda Uganda, officially the Republic of Uganda, is a landlocked country in East Africa. It is bordered to the east by Kenya, to the north by South Sudan, to the west by the Democratic Republic of the Congo, to the south-west by Rwanda, and to the ...
. In July 2019, an infected man travelled to
Goma Goma is a city in the eastern Democratic Republic of the Congo. It is the Capital city, capital and largest city of the North Kivu, North Kivu Province; it is located on the northern shore of Lake Kivu and shares borders with the Bukumu Chiefdo ...
, home to more than two million people. One week later, on 17 July 2019, the WHO declared the Ebola outbreak a global health emergency, the fifth time such a declaration has been made by the organisation. A government spokesman said that half of the Ebola cases are unidentified, and he added that the current outbreak could last up to three years. On 25 June 2020, the second biggest EVD outbreak ever was declared over.


2020 Équateur province

On 1 June 2020, the Congolese health ministry announced a new DRC outbreak of Ebola in
Mbandaka Mbandaka (, formerly known as Coquilhatville in French, or Coquilhatstad in Dutch) is a city in the Democratic Republic of Congo located near the confluence of the Congo and Ruki rivers. It is the capital of Équateur Province. The city was f ...
,
Équateur Province Équateur, French for equator, may refer to: Places * Province of Équateur, a province of the Democratic Republic of the Congo since 2015 * Équateur (former province), a former province of the Democratic Republic of the Congo, 1966–2015 * à ...
, a region along the Congo River. Genome sequencing suggests that this outbreak, the 11th outbreak since the virus was first discovered in the country in 1976, is unrelated to the one in North Kivu Province or the previous outbreak in the same area in 2018. It was reported that six cases had been identified; four of the people had died. It is expected that more people will be identified as surveillance activities increase. By 15 June the case count had increased to 17 with 11 deaths, with more than 2,500 people having been vaccinated. The 11th EVD outbreak was officially declared over on 19 November 2020. By the time the Équateur outbreak ended, it had 130 confirmed cases with 75 recoveries and 55 deaths.


2021


North Kivu

On 7 February 2021, the Congolese health ministry announced a new case of Ebola near Butembo, North Kivu detected a day before. The case was a 42-year-old woman who had symptoms of Ebola in Biena on 1 February 2021. A few days after, she died in a hospital in Butembo. The WHO said that more than 70 people with contact with the woman had been tracked. On 11 February 2021, another woman who had contact with the previous woman died in the same town, and the number of traced contacts increased to 100. A day after, a third case was detected in Butembo. On 3 May 2021, the 12th EVD outbreak was declared over, resulting in 12 cases and six deaths. Heightened surveillance will continue for 90 days after the declaration, in case of resurgence.


Guinea

In February 2021, Sakoba Keita, head of Guinea's national health agency confirmed that three people had died of Ebola in the south-eastern region near the city of Nzérékoré. A further five people also tested positive. Keita also confirmed more testing was underway, and attempts to trace and isolate further cases had begun. On 14 February, the Guinean government declared an Ebola epidemic. The outbreak may have started following reactivation of a latent case in a survivor of an earlier outbreak. As of 4 May 2021, 23 cases were reported, with no new cases or deaths since 3 April 2021. A 42-day countdown period was started on 8 May 2021, and on 19 June, the outbreak was declared over.


Ivory Coast

On 14 August 2021, The Ministry of Health of
Cote d’Ivoire Ivory Coast, also known as Côte d'Ivoire and officially the Republic of Côte d'Ivoire, is a country on the southern coast of West Africa. Its capital city of Yamoussoukro is located in the centre of the country, while its largest city and ...
confirmed the country's first case of Ebola since 1994. This came after the Institut Pasteur in Cote d'Ivoire confirmed the Ebola Virus Disease in samples collected from a patient, who was hospitalized in the commercial capital of
Abidjan Abidjan ( , ; N'Ko script, N'ko: ߊߓߌߖߊ߲߬) is the largest city and the former capital of Ivory Coast. As of the Demographics of Ivory Coast, 2021 census, Abidjan's population was 6.3 million, which is 21.5 percent of the overall population ...
, after arriving from Guinea. However, on 31 August 2021, the WHO found that, after further tests in a laboratory in
Lyon Lyon (Franco-Provençal: ''Liyon'') is a city in France. It is located at the confluence of the rivers Rhône and Saône, to the northwest of the French Alps, southeast of Paris, north of Marseille, southwest of Geneva, Switzerland, north ...
, the patient did not have Ebola. The cause of her disease is still being analyzed.


2022

On 23 April 2022, a case of Ebola was confirmed in the DRC in the Equateur province. The case was a 31-year-old man whose symptoms began on 5 April, but did not seek treatment for over a week. On 21 April, he was admitted to an Ebola treatment centre and died later that day. By 24 May 2022, there were 5 recorded deaths in the DRC. On 15 August, the fifth case was buried, and the outbreak was declared over, 42 days after, on 4 July 2022. In September 2022, Uganda reported 7 cases infected with the Ebola Sudan strain, but by mid-October the count had increased to 63. In November 2022, the outbreak in Uganda continued - still without a vaccine. On 10 January 2023, the outbreak was considered over after no new cases had been reported for 42 days; the outbreak killed nearly 80 people.


Society and culture


Weaponisation

''Ebolavirus'' is classified as a biosafety level 4 agent, as well as a Category A bioterrorism agent by the Centers for Disease Control and Prevention. It has the potential to be weaponised for use in
biological warfare Biological warfare, also known as germ warfare, is the use of biological toxins or Pathogen, infectious agents such as bacteria, viruses, insects, and Fungus, fungi with the intent to kill, harm or incapacitate humans, animals or plants as an ...
, and was investigated by
Biopreparat The All-Union Science Production Association Biopreparat (, , ) was a Soviet agency created in April 1974, which spearheaded the largest and most sophisticated offensive biological warfare program known. It was a vast, ostensibly civilian, netw ...
for such use, but might be difficult to prepare as a
weapon of mass destruction A weapon of mass destruction (WMD) is a biological, chemical, radiological, nuclear, or any other weapon that can kill or significantly harm many people or cause great damage to artificial structures (e.g., buildings), natural structures ( ...
because the virus becomes ineffective quickly in open air. Fake emails pretending to be Ebola information from the WHO or the Mexican government have, in 2014, been misused to spread computer malware. The BBC reported in 2015 that "North Korean state media has suggested the disease was created by the U.S. military as a biological weapon."


Literature

Richard Preston Richard Preston (born August 5, 1954) is a writer for ''The New Yorker'' and bestselling author who has written books about infectious disease, bioterrorism, redwoods and other subjects, as well as fiction. Biography Preston was born in Cambr ...
's 1995
best-selling A bestseller is a book or other media noted for its top selling status, with bestseller lists published by newspapers, magazines, and book store chains. Some lists are broken down into classifications and specialties (novel, nonfiction book, coo ...
book, ''
The Hot Zone ''The Hot Zone: A Terrifying True Story'' is a best-selling 1994 nonfiction thriller by Richard Preston about the origins and incidents involving viral hemorrhagic fevers, particularly ebolaviruses and marburgviruses. The basis of the book ...
'', dramatised the Ebola outbreak in Reston, Virginia.
William Close William Taliaferro Close (June 7, 1924 – January 15, 2009) was an American surgeon who played a major role in stemming a 1976 outbreak of the Ebola virus in Zaire, the first major outbreak of the viral hemorrhagic fever in Central Africa, and p ...
's 1995 ''Ebola: A Documentary Novel of Its First Explosion'' and 2002 ''Ebola: Through the Eyes of the People'' focused on individuals' reactions to the 1976 Ebola outbreak in Zaire.
Tom Clancy Thomas Leo Clancy Jr. (April 12, 1947 â€“ October 1, 2013) was an American novelist. He is best known for his technically detailed espionage and military science, military-science storylines set during and after the Cold War. Seventeen of ...
's 1996 novel, ''
Executive Orders ''Executive Orders'' is a techno-thriller novel, written by Tom Clancy and released on July 1, 1996. It picks up immediately where the final events of '' Debt of Honor'' (1994) left off, and features now- U.S. President Jack Ryan as he tries ...
'', involves a
Middle East The Middle East (term originally coined in English language) is a geopolitical region encompassing the Arabian Peninsula, the Levant, Turkey, Egypt, Iran, and Iraq. The term came into widespread usage by the United Kingdom and western Eur ...
ern terrorist attack on the United States using an airborne form of a deadly Ebola virus strain named "Ebola Mayinga" (see
Mayinga N'Seka Mayinga N'Seka (1954 – October 19, 1976) was a nurse in Zaïre, now Democratic Republic of the Congo. She died from Ebola virus disease during the 1976 Zaire Ebola virus outbreak, 1976 epidemic in Zaïre. She was incorrectly identified as the i ...
). As the Ebola virus epidemic in West Africa developed in 2014, a number of popular self-published and well-reviewed books containing sensational and misleading information about the disease appeared in electronic and printed formats. The authors of some such books admitted that they lacked medical credentials and were not technically qualified to give medical advice. The World Health Organization and the United Nations stated that such misinformation had contributed to the spread of the disease.


Other animals


Wild animals

Ebola has a high mortality rate among primates. Frequent outbreaks of Ebola may have resulted in the deaths of 5,000 gorillas. Outbreaks of Ebola may have been responsible for an 88% decline in tracking indices of observed chimpanzee populations in the 420 km2 Lossi Sanctuary between 2002 and 2003. Transmission among chimpanzees through meat consumption constitutes a significant risk factor, whereas contact between the animals, such as touching dead bodies and grooming, is not. Recovered gorilla carcasses have contained multiple Ebola virus strains, suggesting multiple introductions of the virus. Bodies decompose quickly and carcasses are not infectious after three to four days. Contact between gorilla groups is rare, suggesting that transmission among gorilla groups is unlikely, and that outbreaks result from transmission between viral reservoirs and animal populations.


Domestic animals

In 2012, it was demonstrated that the virus can travel without contact from pigs to nonhuman primates, although the same study failed to achieve transmission in that manner between primates. Dogs may become infected with EBOV but not develop symptoms. Dogs in some parts of Africa
scavenge Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding be ...
for food, and they sometimes eat EBOV-infected animals and also the corpses of humans. A 2005 survey of dogs during an EBOV outbreak found that although they remain asymptomatic, about 32 percent of dogs closest to an outbreak showed a
seroprevalence Seroprevalence is the number of persons in a population who test positive for a specific disease based on serology (blood serum) specimens, often presented as a percent of the total specimens tested or as a proportion per 100,000 persons tested. As ...
for EBOV versus nine percent of those farther away. The authors concluded that there were "potential implications for preventing and controlling human outbreaks."


Reston virus

In late 1989, Hazelton Research Products' Reston Quarantine Unit in
Reston, Virginia Reston is a census-designated place in Fairfax County, Virginia, United States, and a principal city of both Northern Virginia and the Washington metropolitan area. As of the 2020 U.S. census, Reston's population was 63,226. Founded in 1964, Rest ...
, had an outbreak of fatal illness amongst certain lab monkeys. This lab outbreak was initially diagnosed as simian haemorrhagic fever virus (SHFV) and occurred amongst a shipment of
crab-eating macaque The crab-eating macaque (''Macaca fascicularis''), also known as the long-tailed macaque or cynomolgus macaque, is a cercopithecine primate native to Southeast Asia. As a synanthropic species, the crab-eating macaque thrives near human settlem ...
monkeys imported from the Philippines. Hazelton's veterinary pathologist in Reston sent tissue samples from dead animals to the
United States Army Medical Research Institute of Infectious Diseases The United States Army Medical Research Institute of Infectious Diseases (USAMRIID; ) is the United States Army's main institution and facility for defensive research into countermeasures against biological warfare. It is located on Fort D ...
(USAMRIID) at
Fort Detrick, Maryland Fort Detrick () is a United States Army Futures Command installation located in Frederick, Maryland. Fort Detrick was the center of the U.S. biological weapons program from 1943 to 1969. Since the discontinuation of that program, it has hosted m ...
, where an
ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay is a solid-phase type of enzyme immunoassay (EIA) to detect the presence of ...
test indicated the antibodies present in the tissue were a response to Ebola virus and not SHFV. An electron microscopist from USAMRIID discovered
filoviruses ''Filoviridae'' () is a family of single-stranded negative-sense RNA viruses in the order ''Mononegavirales''. Two members of the family that are commonly known are Ebola virus and Marburg virus. Both viruses, and some of their lesser known rela ...
similar in appearance, in crystalloid aggregates and as single filaments with a shepherd's hook, to Ebola in the tissue samples sent from Hazelton Research Products' Reston Quarantine Unit. A
US Army The United States Army (USA) is the primary land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of the United Stat ...
team headquartered at USAMRIID
euthanised Animal euthanasia (euthanasia from ; "good death") is the act of killing an animal humanely, most commonly with injectable drugs. Reasons for euthanasia include incurable (and especially painful) conditions or diseases, lack of resources to con ...
the surviving monkeys, and brought all the dead monkeys to Fort Detrick for study by the Army's veterinary pathologists and virologists, and eventual disposal under safe conditions. Blood samples were taken from 178 animal handlers during the incident. Of those, six animal handlers eventually seroconverted, including one who had cut himself with a bloody scalpel. Despite its status as a Level‑4 organism and its apparent
pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...
icity in monkeys, when the handlers did not become ill, the CDC concluded that the virus had a very low pathogenicity to humans. The Philippines and the United States had no previous cases of Ebola infection, and upon further isolation, researchers concluded it was another strain of Ebola, or a new filovirus of Asian origin, which they named ''
Reston ebolavirus Reston virus (RESTV) is one of six known viruses within the genus ''Ebolavirus''. Reston virus causes Ebola virus disease in non-human primates; out of all 6 ebolaviruses, it is one of the only two not known to cause disease in humans, but has ca ...
'' (RESTV) after the location of the incident. Reston virus (RESTV) can be transmitted to pigs. Since the initial outbreak it has since been found in nonhuman
primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...
s in Pennsylvania, Texas, and Italy, where the virus had infected pigs. According to the WHO, routine cleaning and disinfection of pig (or monkey) farms with
sodium hypochlorite Sodium hypochlorite is an alkaline inorganic chemical compound with the formula (also written as NaClO). It is commonly known in a dilute aqueous solution as bleach or chlorine bleach. It is the sodium salt of hypochlorous acid, consisting of ...
or detergents should be effective in inactivating the ''Reston ebolavirus''. Pigs that have been infected with RESTV tend to show
symptoms Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...
of the disease.


Research


Treatments

, no medication has been proven safe and effective for treating Ebola. By the time the
Ebola virus epidemic in West Africa The 2013–2016 epidemic of Ebola virus disease, centered in West Africa, was the most widespread outbreak of the disease in history. It caused major loss of life and socioeconomic disruption in the region, mainly in Guinea, Liberia and S ...
began in 2013, there were at least nine different candidate treatments. Several trials were conducted in late 2014, and early 2015, but some were abandoned due to lack of efficacy or lack of people to study. , two experimental treatments known as
atoltivimab/maftivimab/odesivimab Atoltivimab/maftivimab/odesivimab, sold under the brand name INMAZEB, is a fixed-dose combination of three monoclonal antibodies for the treatment of ''Zaire ebolavirus'' (Ebola virus). It was developed by Regeneron Pharmaceuticals and contain ...
and ansuvimab were found to be 90% effective.


Diagnostic tests

The diagnostic tests currently available require specialised equipment and highly trained personnel. Since there are few suitable testing centres in West Africa, this leads to delay in diagnosis. On 29 November 2014, a new 15-minute Ebola test was reported that if successful, "not only gives patients a better chance of survival, but it prevents transmission of the virus to other people." The new equipment, about the size of a laptop and solar-powered, allows testing to be done in remote areas. On 29 December 2014, the U.S.
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
(FDA) approved the LightMix Ebola Zaire rRT-PCR test for patients with symptoms of Ebola.


Disease models

Animal models and in particular non-human primates are being used to study different aspects of Ebola virus disease. Developments in
organ-on-a-chip An organ-on-a-chip (OOC) is a multi-channel 3D microfluidic cell culture, integrated circuit (chip) that simulates the activities, mechanics and physiological response of an entire organ or an organ system. It constitutes the subject matter of si ...
technology have led to a chip-based model for Ebola haemorrhagic syndrome.


See also

* Bibliography of Ebola


Notes


References

* ''The article uses public domain text from the CDC as cited.''


Bibliography

*


Further reading

* * * * * * *


External links


WHO fact sheet on Ebola

Ebola (Ebola Virus Disease)
nbsp;– Centers for Disease Control and Prevention, Viral Special Pathogens Branch.
Videos: Ebola outbreak response
nbsp;– World Health Organization. *
Ebola: What You Need to Know
nbsp;– ''
Scientific American ''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it, with more than 150 Nobel Pri ...
'' articles related to Ebola; note these are general reading articles, they are not scientific peer-reviewed research articles. {{Authority control Animal viral diseases Articles containing video clips Bat virome Biological agents Health in Africa Hemorrhagic fevers Wikipedia medicine articles ready to translate Wikipedia infectious disease articles ready to translate Sexually transmitted diseases and infections Tropical diseases Virus-related cutaneous conditions West African Ebola virus epidemic Wikipedia pages referenced by the press Zoonotic viral diseases Vaccine-preventable diseases so:Ebola virus disease