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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 animal and human illnesses in which fever and hemorrhage are caused by a viral infection. VHFs may be caused by five distinct families of RNA viruses: the families ''Filoviridae'', ''Flavi ...
in humans and other
primate Primates are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...
s, caused by
ebolavirus The genus ''Ebolavirus'' (- or ; - or ) is a virological taxon included in the family ''Filoviridae'' (filament-shaped viruses), order ''Mononegavirales''. The members of this genus are called ebolaviruses, and encode their genome in the form ...
es. Symptoms typically start anywhere between two days and three weeks after becoming infected with the virus. The first symptoms are usually
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
,
sore throat Sore throat, also known as throat pain, is pain or irritation of the throat. Usually, causes of sore throat include * viral infections * group A streptococcal infection (GAS) bacterial infection * pharyngitis (inflammation of the throat) * t ...
,
muscle pain Myalgia (also called muscle pain and muscle ache in layman's terms) is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another li ...
, and
headache Headache 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. Headaches can occur as a resul ...
s. These are usually followed by
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, 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, gastroenteri ...
,
diarrhoea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...
,
rash A rash is a change of the human skin which 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, cr ...
and decreased
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
and
kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; bloo ...
function, at which point, some people begin to bleed both internally and externally. The disease 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 six and 16 days after the first symptoms appear. Early treatment of symptoms increases the survival rate considerably compared to late start. The virus spreads through direct contact with
body fluid Body fluids, bodily fluids, or biofluids, sometimes body liquids, are liquids within the human body. In lean healthy adult men, the total body water is about 60% (60–67%) of the total body weight; it is usually slightly lower in women (52-55%) ...
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 in th ...
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 the disease spreading through the air between humans or other
primate Primates are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...
s. After a person recovers from Ebola, their
semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen ...
or
breast milk Breast milk (sometimes spelled as breastmilk) or mother's milk is milk produced by mammary glands located in the breast of a human female. Breast milk is the primary source of nutrition for newborns, containing fat, protein, carbohydrates (lac ...
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 ( bats). 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 ...
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 infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or deat ...
, cholera,
typhoid fever Typhoid fever, also known as typhoid, is a disease caused by '' Salmonella'' serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over severa ...
,
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, headache, and neck stiffness. Other symptoms include confusion ...
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 essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
, viral antibodies 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 persons 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 final disposition of a dead body through burning. Cremation may serve as a funeral or post-funeral rite and as an alternative to burial. In some countries, including India and Nepal, cremation on an open-air pyre ...
or burial. Samples of body fluids and tissues from people with the disease should be handled with extreme caution. Prevention measures include 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, or other harmful and unwanted substances stuck to the h ...
when around a person with the disease, and limiting the spread of the disease from infected animals to humans – by wearing protective clothing while handling potentially infected
bushmeat Bushmeat is meat from wildlife species that are hunted for human consumption, most often referring to the meat of game in Africa. Bushmeat represents a primary source of animal protein and a cash-earning commodity for inhabitants of humid tro ...
, and by cooking bushmeat thoroughly before eating it. 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 be ...
was approved in the United States 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 contains atoltivimab, maftivimab, and odesivimab-ebg ...
and
ansuvimab Ansuvimab, sold under the brand name Ebanga, is a monoclonal antibody medication for the treatment of ''Zaire ebolavirus'' (Ebolavirus) infection. The most common symptoms include fever, tachycardia (fast heart rate), diarrhea, vomiting, hypote ...
) are associated with improved outcomes. Supportive efforts also improve outcomes. These include
oral rehydration therapy Oral rehydration therapy (ORT) 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 salts, specifically sodium and potassium. Oral rehydra ...
(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 nutrie ...
, 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

The disease was first identified in 1976, in two simultaneous outbreaks: one in Nzara (a town in
South Sudan South Sudan (; din, Paguot Thudän), officially the Republic of South Sudan ( din, Paankɔc Cuëny Thudän), is a landlocked country in East Africa. It is bordered by Ethiopia, Sudan, Central African Republic, Democratic Republic of the ...
) and the other in
Yambuku Yambuku is a small village in Mongala Province in northern Democratic Republic of the Congo. It was the center of the first documented outbreak of Ebola virus disease, in 1976, with the World Health Organization identifying a man from Yambuku as ...
(
the Democratic Republic of the Congo The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
), a village near the
Ebola River The Ebola River ( or ), also commonly known by its indigenous 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 F ...
, from which the disease takes its name. Ebola outbreaks occur intermittently in tropical regions of sub-Saharan Africa. Between 1976 and 2012, according to the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...
, 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 radiation, and when symptoms and signs are first apparent. In a typical infectious disease, the in ...
) 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 symptom ...
-like stage characterised by
fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...
,
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
,
weakness Weakness is a symptom of a number of different 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, i ...
, decreased appetite,
muscular pain Myalgia (also called muscle pain and muscle ache in layman's terms) is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another lik ...
,
joint pain Arthralgia (from Greek ''arthro-'', joint + ''-algos'', pain) literally means ''joint pain''. Specifically, arthralgia is a symptom of injury, infection, illness (in particular arthritis), or an allergic reaction to medication. According to MeSH, ...
, headache, and sore throat. The fever is usually higher than . This is often followed by nausea, vomiting,
diarrhoea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...
, abdominal pain, and sometimes
hiccups A hiccup (scientific name ''singultus'', from a Latin word meaning "to catch one's breath while sobbing"; also spelled hiccough) is an involuntary contraction ( myoclonic jerk) of the diaphragm that may repeat several times per minute. The hi ...
. The combination of severe vomiting and diarrhoea often leads to severe
dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mi ...
. Next,
shortness of breath Shortness of breath (SOB), also medically 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 di ...
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 ...
may occur, along with swelling,
headaches Headache 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. Headaches can occur as a resul ...
, and
confusion In medicine, confusion is the quality or 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, flat ...
, 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 is always an important sign. It can be confused with hemoptysis (coughing up blood) or epistaxis (nosebleed), which are more common. The source is generally the upper gastrointestinal tract, typically abo ...
, 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 origi ...
. Bleeding into the skin may create
petechia A petechia () is a small red or purple spot (≤4 mm in diameter) that can appear on the skin, conjunctiva, retina, and mucous membranes which is caused by haemorrhage of capillaries. The word is derived from Italian , 'freckle,' of obscure origin ...
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 clos ...
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 b ...
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 digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans a ...
. 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.


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 respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...
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 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 virological taxon included in the family ''Filoviridae'' (filament-shaped viruses), order ''Mononegavirales''. The members of this genus are called ebolaviruses, and encode their genome in the form ...
''. 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 The species ''Sudan ebolavirus'' is a virological taxon included in the genus ''Ebolavirus'', family ''Filoviridae'', order '' Mononegavirales''. The species has a single virus member, Sudan virus (SUDV). The members of the species are called S ...
(SUDV),
Taï Forest virus Taï is a town in southwestern Ivory Coast. It is a sub-prefecture of and the seat of Taï Department in Cavally Region, Montagnes District. Taï is also a commune. The town is between Taï National Park and the Cavally River. The river—which ...
(TAFV) and one simply called
Ebola virus ''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 hemorrhagic fever in humans and o ...
(EBOV, formerly Zaire Ebola virus). EBOV, species ''
Zaire ebolavirus ''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 hemorrhagic fever in humans and o ...
'', 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; unlike the other five ebolaviruses, it is not known to cause disease in humans, but has caused asymp ...
(RESTV) and Bombali virus (BOMV), are not thought to cause disease in humans, but have caused disease in other primates. All five 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 prim ...
es.


Virology

Ebolaviruses contain single-stranded, non-infectious
RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
genome In the fields of molecular biology and genetics, 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 ...
s. ''Ebolavirus'' genomes contain seven
gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
s including
3'-UTR In molecular genetics, the three prime untranslated region (3′-UTR) is the section of messenger RNA (mRNA) that immediately follows the translation termination codon. The 3′-UTR often contains regulatory regions that post-transcriptionally ...
-''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 called ...
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 birth to reproduction ending with the production of the offspring * Life-cycle hypothesi ...
is thought to begin with a virion attaching to specific
cell-surface receptors The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (the ...
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 pr ...
, or
integrin Integrins are transmembrane receptors that facilitate 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, ...
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 endocytic membrane transport pathway originating from the trans Golgi network. Molecules or ligands internalized from the plasma membrane c ...
s and
lysosome A lysosome () is a membrane-bound organelle found in many animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, of both its membrane ...
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 may ...
. 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 synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the ...
, 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 synthesizing a protein. mRNA is created during the ...
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 (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (the ...
. Virions
bud In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be speci ...
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 human body. In lean healthy adult men, the total body water is about 60% (60–67%) of the total body weight; it is usually slightly lower in women (52-55%) ...
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 an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen ...
. The WHO states that only people who are very sick are able to spread Ebola disease in saliva, and the virus has not been reported to be transmitted through sweat. Most people spread the virus through blood,
feces Feces ( or faeces), known colloquially and in slang as poo and poop, 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 large intestine. Feces contain a rela ...
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 lower end of a tube or other surface boundary, producing a hanging drop called a pendant d ...
; 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. 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 (in its modern form with chemicals) to forestall decomposition. This is usually done to make the deceased suitable for public or private viewing as part of the funeral ...
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 are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter includin ...
, 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 genus ''Papio'', one of the 23 genera of Old World monkeys. There are six species of baboon: the hamadryas baboon, the Guinea baboon, the olive baboon, the yellow baboon, the Kinda baboon and the chac ...
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 ...
( chimpanzees and
gorilla Gorillas are herbivorous, predominantly ground-dwelling 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 ...
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 is used to refer to many species of even-toed ruminant that are indigenous to various regions in Africa and Eurasia. Antelope comprise a wastebasket taxon defined as any of numerous Old World grazing and browsing hoofed mamm ...
). 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 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 lives and re ...
for Ebola has yet to be confirmed; however, bats 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'') were found to possibly carry the virus without getting sick. , whether other animals are involved in its spread is not known. Plants,
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
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 lower jaws. About 40% of all mammal species are roden ...
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 (; ; snq, Ngabu), officially the Gabonese Republic (french: République gabonaise), is a country on the west coast of Central Africa. Located on the equator, it is bordered by Equatorial Guinea to the northwest, Cameroon to the north ...
and the Republic of the Congo, 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, with a population exceeding 165 million pe ...
, 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 (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
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 Peters's mouse (''Mus setulosus'') is a species of rodent in the family Muridae. It is found in Benin, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Ethiopia, Gabon ...
'' and ''
Praomys ''Praomys'' is a genus of rodent in the family Muridae endemic to Sub-Saharan Africa. It contains the following species: * ''Praomys coetzeei'' * Dalton's mouse, ''Praomys daltoni'' * De Graaff's soft-furred mouse, ''Praomys degraaffi'' * Dero ...
'') 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 diffe ...
(''
Sylvisorex ollula The greater forest shrew (''Sylvisorex ollula'') is a species of mammal in the family Soricidae found in Cameroon, the Central African Republic, the Republic of the Congo, Equatorial Guinea, Gabon, and Nigeria. Its natural habitat is subtropical ...
'') collected from the
Central African Republic The Central African Republic (CAR; ; , RCA; , or , ) is a landlocked country in Central Africa. It is bordered by Chad to the north, Sudan to the northeast, South Sudan to the southeast, the DR Congo to the south, the Republic of the C ...
. 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 of a forest or stand of trees from land that is then land conversion, converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban area, urban ...
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 Western 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 an ...
. Index cases of EVD have often been close to recently deforested lands.


Pathophysiology

Like other filoviruses, EBOV replicates very efficiently in many
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
, 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 conventional dendritic cells. As a part of the vertebrate innate immune system monocytes also i ...
s, macrophages,
dendritic cell Dendritic cells (DCs) are antigen-presenting cells (also known as ''accessory cells'') of the mammalian immune system. Their 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, b ...
,
fibroblast A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells of ...
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 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 rest of the ves ...
(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 inc ...
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, lymphatic or lymphoi ...
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 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 usually confers ...
. Other types of
white blood cell White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...
s, such as
lymphocyte A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic ad ...
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 structures of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away from ...
injury can be attributed to EBOV
glycoprotein Glycoproteins are proteins which contain oligosaccharide 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 as g ...
s. This damage occurs due to the synthesis of Ebola virus
glycoprotein Glycoproteins are proteins which contain oligosaccharide 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 as g ...
(GP), which reduces the availability of specific
integrin Integrins are transmembrane receptors that facilitate 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, ...
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, urethra, vag ...
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 potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanis ...
due to excessive
tissue factor Tissue factor, also called platelet tissue factor, factor III, or CD142, is a protein encoded by the ''F3'' gene, present in subendothelial tissue and leukocytes. Its role in the clotting process is the initiation of thrombin formation from the ...
production by macrophages and monocytes. After infection, a secreted
glycoprotein Glycoproteins are proteins which contain oligosaccharide 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 as g ...
, 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 In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' has ...
that interferes with the signalling of
neutrophils Neutrophils (also known as neutrocytes or heterophils) are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying i ...
, another type of white blood cell. This enables the virus to evade the immune system by inhibiting early steps of neutrophil activation.


Immune system evasion

Filoviral infection also interferes with proper functioning of the
innate immune system The innate, or nonspecific, immune system is one of the two main immunity strategies (the other being the adaptive immune system) in vertebrates. The innate immune system is an older evolutionary defense strategy, relatively speaking, and is th ...
. 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 (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. Wheelock ...
. 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) responsible for the type-1 interferon (IFN1) response. RIG-I is an essential molecule in the innate immune system for recognizing cells that have been infect ...
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 fun ...
) 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 ...
,
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 ...
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 expresse ...
) 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. IR ...
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 cyto ...
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 al ...
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). STAT2 s ...
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 transaminase (ALT) is a transaminase enzyme (). It is also called alanine aminotransferase (ALT or ALAT) and was formerly called serum glutamate-pyruvate transaminase or serum glutamic-pyruvic transaminase (SGPT) and was first characte ...
(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 (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 ''extrinsic'' pathway and common pathway of coagulation. This blood test is al ...
,
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 on someone to assess their platelets function. 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 bleed ...
. 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 accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a ...
. The specific diagnosis of EVD is confirmed by isolating the virus, detecting its
RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
or proteins, or detecting antibodies against the virus in a person's blood. Isolating the virus by cell culture, detecting the viral RNA by
polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...
(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 uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...
(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 one of several isotypes of antibody (also known as immunoglobulin) that are produced by vertebrates. IgM is the largest antibody, and it is the first antibody to appear in the response to initial exposure to an antig ...
are detectable two days after symptom onset and
IgG antibodies Immunoglobulin G (Ig G) 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 a ...
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) is a laboratory technique of molecular biology based on the polymerase chain reaction (PCR). It monitors the amplification of a targeted DNA molecule during the PCR (i.e., in real ...
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 infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or deat ...
and
dengue fever Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. These may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic ...
. The symptoms are also similar to those of other viral haemorrhagic fevers such as
Marburg virus disease Marburg virus disease (MVD; formerly Marburg hemorrhagic fever) is a viral hemorrhagic fever in humans and primates caused by either of the two Marburgviruses: Marburg virus (MARV) and Ravn virus (RAVV). Its clinical symptoms are very similar to ...
, Crimean–Congo haemorrhagic fever, and
Lassa fever Lassa fever, also known as Lassa hemorrhagic fever (LHF), is a type of viral hemorrhagic fever caused by the Lassa virus. Many of those infected by the virus do not develop symptoms. When symptoms occur they typically include fever, weakness, ...
. The complete differential diagnosis is extensive and requires consideration of many other infectious diseases such as
typhoid fever Typhoid fever, also known as typhoid, is a disease caused by '' Salmonella'' serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over severa ...
,
shigellosis Shigellosis 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 stools even when the bowels are ...
, rickettsial diseases, cholera,
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is foll ...
,
borreliosis Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the ''Borrelia'' bacterium, which is spread by ticks in the genus ''Ixodes''. The most common sign of infection is an expanding red rash, known as erythema migran ...
, EHEC enteritis,
leptospirosis Leptospirosis is a blood infection caused by the bacteria '' Leptospira''. Signs and symptoms can range from none to mild (headaches, muscle pains, and fevers) to severe ( bleeding in the lungs or meningitis). Weil's disease, the acute, seve ...
,
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 Plague or The Plague may refer to: Agriculture, fauna, and medicine *Plague (disease), a disease caused by ''Yersinia pestis'' * An epidemic of infectious disease (medical or agricultural) * A pandemic caused by such a disease * A swarm of pes ...
,
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 type of '' Candida'' (a type of 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 mouth ...
,
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 dise ...
,
visceral In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...
leishmaniasis Leishmaniasis is a wide array of clinical manifestations caused by parasites of the trypanosome genus '' Leishmania''. It is generally spread through the bite of phlebotomine sandflies, '' Phlebotomus'' and ''Lutzomyia'', and occurs most f ...
, measles, and
viral hepatitis Viral hepatitis is liver inflammation due to a viral infection. It may present in acute form as a recent infection with relatively rapid onset, or in chronic form. The most common causes of viral hepatitis are the five unrelated hepatotropic vi ...
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 a ...
,
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 o ...
,
snake envenomation A snakebite is an injury caused by the bite of a snake, especially a venomous snake. A common sign of a bite from a venomous snake is the presence of two puncture wounds from the animal's fangs. Sometimes venom injection from the bite may occu ...
,
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 potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism ...
deficiencies/platelet disorders,
thrombotic thrombocytopenic purpura Thrombotic thrombocytopenic purpura (TTP) is a blood disorder that results in blood clots forming in small blood vessels throughout the body. This results in a low platelet count, low red blood cells due to their breakdown, and often kidney, h ...
,
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 skin, mucous membranes, ...
,
Kawasaki disease Kawasaki disease 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, where blood vessels become inflamed throughout the body. The fever typically lasts for more t ...
, and
warfarin Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to prevent blood clots such as deep vein thrombosis and pulmonary embolism, and to prevent ...
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 be ...
,
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 .


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, and is headquartered in Atlanta, Georg ...
(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, ...
(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 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 bacterial spores; it is less effective than ...
. 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 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 or The Doctor may refer to: Personal titles * Doctor (title), the holder of an accredited academic degree * A medical practitioner, including: ** Physician ** Surgeon ** Dentist ** Veterinary physician ** Optometrist *Other role ...
.


Disinfection

Ebolaviruses can be eliminated with heat (heating for 30 to 60 minutes at 60 °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 bacterial spores; it is less effective than s ...
surfaces, some lipid solvents such as some alcohol-based products, detergents, sodium hypochlorite (bleach) or
calcium hypochlorite Calcium hypochlorite is an inorganic compound with formula Ca(OCl)2. It is the main active ingredient of commercial products called bleaching powder, chlorine powder, or chlorinated lime, used for water treatment and as a bleaching agent. Th ...
(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 specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...
. 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 or handwash and water to remove viruses/bacteria/microorganisms, dirt, grease, or other harmful and unwanted substances stuck to the hand ...
using soap and water.


Bushmeat

Bushmeat Bushmeat is meat from wildlife species that are hunted for human consumption, most often referring to the meat of game in Africa. Bushmeat represents a primary source of animal protein and a cash-earning commodity for inhabitants of humid tro ...
, 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 ritual Burial, also known as interment or inhumation, is a method of final disposition whereby a dead body is placed into the ground, sometimes with objects. This is usually accomplished by excavating a pit or trench, placing the deceased and objec ...
s, 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 been ...
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 persons 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 contains atoltivimab, maftivimab, and odesivimab-ebg ...
and
ansuvimab Ansuvimab, sold under the brand name Ebanga, is a monoclonal antibody medication for the treatment of ''Zaire ebolavirus'' (Ebolavirus) infection. The most common symptoms include fever, tachycardia (fast heart rate), diarrhea, vomiting, hypote ...
) 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 federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
(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 federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
(FDA) approved atoltivimab/maftivimab/odesivimab with an
indication Indication may refer to: * A synonym for sign * Human interface, highlighting the single object pointed to as a cursor is moved, without any other user action such as clicking, is indication * Indication (medicine). A valid reason to use a certain ...
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 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 and simple to chronic and challenging. Most physicians and other health professionals p ...
, and treatment for
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
,
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
, and
anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil Turmoil may refer to: * ''Turmoil'' (1984 video game), a 1984 video game released by Bug-Byte * ''Turmoil'' (2016 video game), a 2016 indie oil tycoon video ...
. The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...
(WHO) recommends avoiding
aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat in ...
or
ibuprofen Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that is used for treating pain, fever, and inflammation. This includes painful menstrual periods, migraines, and rheumatoid arthritis. It may also be used to close a patent ductus ...
for pain management, due to the risk of bleeding associated with these medications. Blood products such as
packed red blood cells Packed red blood cells, also known as packed cells, are red blood cells that have been separated for blood transfusion. The packed cells are typically used in anemia that is either causing symptoms or when the hemoglobin is less than usually 70� ...
,
platelet Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby i ...
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 th ...
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. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the trea ...
in an effort to prevent disseminated intravascular coagulation 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 potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism ...
to decrease bleeding.
Antimalarial medication Antimalarial medications or simply antimalarials are a type of antiparasitic chemical agent, often naturally derived, that can be used to treat or to prevent malaria, in the latter case, most often aiming at two susceptible target groups, young c ...
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 bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...
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, also 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 pro ...
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 may be needed for
kidney failure Kidney failure, also known as end-stage kidney disease, 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 failure is classified as eit ...
, and
extracorporeal membrane oxygenation Extracorporeal membrane oxygenation (ECMO), also known as extracorporeal life support (ECLS), is an extracorporeal technique of providing prolonged cardiac and respiratory support to persons whose heart and lungs are unable to provide an adequ ...
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 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. If an infected person survives, recovery may be quick and complete. Prolonged cases are often complicated by the occurrence of long-term problems, such as inflammation of the testicles,
joint pains Arthralgia (from Greek ''arthro-'', joint + ''-algos'', pain) literally means ''joint pain''. Specifically, arthralgia is a symptom of injury, infection, illness (in particular arthritis), or an allergic reaction to medication. According to MeSH, ...
, fatigue, hearing loss, mood and sleep disturbances,
muscular pain Myalgia (also called muscle pain and muscle ache in layman's terms) is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another lik ...
, abdominal pain,
menstrual abnormalities A menstrual disorder is characterized as any abnormal condition with regards to a person's menstrual cycle. There are many different types of menstrual disorders that vary with signs and symptoms, including pain during menstruation, heavy bleeding, ...
,
miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the death of an embryo or fetus before it is able to survive independently. Miscarriage before 6 weeks of gestation is defined by ESHRE as biochemical ...
s,
skin peeling Desquamation occurs when the outermost layer of a tissue, such as the skin, is shed. The term is . Physiologic desquamation Keratinocytes are the predominant cells of the epidermis, the outermost layer of the skin. Living keratinocytes reside in ...
, 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 scarr ...
. 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 impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...
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, headache, and neck stiffness. Other symptoms include confusion ...
has been reported many months after recovery, . A study of 44 survivors of the Ebola virus in
Sierra Leone Sierra Leone,)]. officially the Republic of Sierra Leone, is a country on the southwest coast of West Africa. It is bordered by Liberia to the southeast and Guinea surrounds the northern half of the nation. Covering a total area of , Sierra ...
reported musculoskeletal pain in 70%, headache in 48%, and eye problems in 14%.


Epidemiology

The disease typically occurs in outbreaks in tropical regions of Sub-Saharan Africa. 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 Western 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,
Sierra Leone Sierra Leone,)]. officially the Republic of Sierra Leone, is a country on the southwest coast of West Africa. It is bordered by Liberia to the southeast and Guinea surrounds the northern half of the nation. Covering a total area of , Sierra ...
, and
Liberia Liberia (), officially the Republic of Liberia, is a country on the West African coast. It is bordered by Sierra Leone to its northwest, Guinea to its north, Ivory Coast to its east, and the Atlantic Ocean to its south and southwest. It ...
.


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), and was caused by
Sudan virus The species ''Sudan ebolavirus'' is a virological taxon included in the genus ''Ebolavirus'', family ''Filoviridae'', order '' Mononegavirales''. The species has a single virus member, Sudan virus (SUDV). The members of the species are called S ...
(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 (french: République du Zaïre, link=no, ), was a Congolese state from 1971 to 1997 in Central Africa that was previously and is now again known as the Democratic Republic of the Congo. Zaire was, ...
.


Zaire

On 26 August 1976, the second outbreak of EVD began in
Yambuku Yambuku is a small village in Mongala Province in northern Democratic Republic of the Congo. It was the center of the first documented outbreak of Ebola virus disease, in 1976, with the World Health Organization identifying a man from Yambuku as ...
, a small rural village in
Mongala District Mongala District (french: District du Mongala, nl, District Mongala) 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 p ...
in northern
Zaire Zaire (, ), officially the Republic of Zaire (french: République du Zaïre, link=no, ), was a Congolese state from 1971 to 1997 in Central Africa that was previously and is now again known as the Democratic Republic of the Congo. Zaire was, ...
(now known as the
Democratic Republic of the Congo The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
). This outbreak was caused by EBOV, formerly designated ''Zaire ebolavirus'', a different member of the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
''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; ; , RCA; , or , ) is a landlocked country in Central Africa. It is bordered by Chad to the north, Sudan to the northeast, South Sudan to the southeast, the DR Congo to the south, the Republic of the C ...
, after visiting the
Ebola River The Ebola River ( or ), also commonly known by its indigenous 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 F ...
between 12 and 22 August. He was originally believed to have
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or deat ...
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 declared the entire region, including Yambuku and the country's capital, Kinshasa, a quarantine zone. No-one was permitted to enter or leave the area, and roads, waterways, and airfields were placed under martial law. Schools, businesses and social organisations were closed. The initial response was led by Congolese doctors, including Jean-Jacques Muyembe-Tamfum, one of the discoverers of Ebola. Muyembe took a blood sample from a Belgian nun; this sample would eventually be used by Peter Piot 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 (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 Province in northern Democratic Republic of the Congo. It was the center of the first documented outbreak of Ebola virus disease, in 1976, with the World Health Organization identifying a man from Yambuku as ...
, 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, was later identified as a new type of virus related to the genus ''Marburgvirus''. Virus strain samples isolated from both outbreaks were named "Ebola virus" after the
Ebola River The Ebola River ( or ), also commonly known by its indigenous 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 F ...
, 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 (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
, DRC), in 1995, affecting 315 and killing 254. In 2000, Uganda 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 ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
''Ebolavirus'' outbreak to date. In 2004, a Russian scientist died from Ebola after Needlestick injury, 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 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 ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
''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 hunted by local villagers around the towns of Isiro and Viadana. In 2014, an outbreak occurred in the DRC. Whole genome sequencing, Genome-sequencing showed that this outbreak was not related to the West Africa Ebola virus outbreak, 2014–15 West Africa Ebola virus outbreak, but was the same EBOV 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 (french: République du Zaïre, link=no, ), was a Congolese state from 1971 to 1997 in Central Africa that was previously and is now again known as the Democratic Republic of the Congo. Zaire was, ...
.


2013–2016 West Africa

In March 2014, the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...
(WHO) reported a major Ebola outbreak in Guinea, 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 its northwest, Guinea to its north, Ivory Coast to its east, and the Atlantic Ocean to its south and southwest. It ...
and
Sierra Leone Sierra Leone,)]. officially the Republic of Sierra Leone, is a country on the southwest coast of West Africa. It is bordered by Liberia to the southeast and Guinea surrounds the northern half of the nation. Covering a total area of , Sierra ...
. 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 or The Doctor may refer to: Personal titles * Doctor (title), the holder of an accredited academic degree * A medical practitioner, including: ** Physician ** Surgeon ** Dentist ** Veterinary physician ** Optometrist *Other role ...
reported the situation in Liberia's capital, Monrovia, 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 (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 and tested positive for Ebola on 23 October. The person recovered and was discharged from Bellevue Hospital on 11 November. On 24 December 2014, a laboratory in Atlanta, Georgia reported that a technician had been exposed to Ebola. On 29 December 2014, Pauline Cafferkey, a British nurse who had just returned to Glasgow from Sierra Leone, was diagnosed with Ebola at Glasgow's Gartnavel General Hospital. After initial treatment in Glasgow, she was transferred by air to RAF Northolt, then to the specialist high-level isolation unit at the Royal Free Hospital in London 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, Iboko, and Wangata areas in Equateur province, including in the large city of Mbandaka. The DRC Ministry of Public Health approved the use of an experimental vaccine. On 13 May 2018, WHO Director-General Tedros Adhanom Ghebreyesus visited Bikoro. Reports emerged that maps of the area were inaccurate, not so much hampering medical providers as epidemiologists 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 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, Democratic Republic of the Congo, 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. In July 2019, an infected man travelled to Goma, home to more than two million people. One week later, on 17 July 2019, the WHO declared the Ebola outbreak a Public Health Emergency of International Concern, 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, Équateur Province, 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, Dr 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 viral latency, 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 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, after arriving from Guinea. However, on 31 August 2021, the WHO found that, after further tests in a laboratory in Lyon, 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, 2022 Uganda Ebola outbreak, Uganda reported 7 cases infected with the Ebola Sudan strain, but by mid-October the count had increased to 63. In November 2022 (present), the outbreak in Uganda continued - still without a vaccine.


Society and culture


Weaponisation

''Ebolavirus'' is classified as a Biosafety level#Levels, biosafety level 4 agent, as well as a Bioterrorism#Category 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, and was investigated by Biopreparat for such use, but might be difficult to prepare as a weapon of mass destruction 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's 1995 best-selling book, ''The Hot Zone'', dramatised the Ebola outbreak in Reston, Virginia. William Close'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's 1996 novel, ''Executive Orders'', involves a Middle Eastern terrorist attack on the United States using an airborne form of a deadly Ebola virus strain named "Ebola Mayinga" (see Mayinga N'Seka). 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 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 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, 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 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 (USAMRIID) at Fort Detrick, Maryland, where an ELISA test indicated the antibodies present in the tissue were a response to Ebola virus and not SHFV. An electron microscopist from USAMRIID discovered filoviruses 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 team headquartered at USAMRIID Euthanisia, euthanised 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 seroconversion, seroconverted, including one who had cut himself with a bloody scalpel. Despite its status as a Biosafety level 4, Level‑4 organism and its apparent pathogenicity 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'' (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 are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...
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 or detergents should be effective in inactivating the ''Reston ebolavirus''. Pigs that have been infected with RESTV tend to show symptoms 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 Western 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 contains atoltivimab, maftivimab, and odesivimab-ebg ...
and
ansuvimab Ansuvimab, sold under the brand name Ebanga, is a monoclonal antibody medication for the treatment of ''Zaire ebolavirus'' (Ebolavirus) infection. The most common symptoms include fever, tachycardia (fast heart rate), diarrhea, vomiting, hypote ...
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 federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
(FDA) approved the LightMix Ebola Zaire Reverse transcription polymerase chain reaction, 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 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

* * * * * * * *


External links


Ebola (Ebola Virus Disease)
nbsp;– Centers for Disease Control and Prevention, Viral Special Pathogens Branch.
Health topics: Ebola virus disease
nbsp;– World Health Organization.
Videos: Ebola outbreak response
nbsp;– World Health Organization. *
Ebola: What You Need to Know
nbsp;– ''Scientific American'' articles related to Ebola; note these are general reading articles, they are not scientific peer-reviewed research articles. {{Authority control Ebola, Animal viral diseases Arthropod-borne viral fevers and viral haemorrhagic fevers Articles containing video clips Bat virome Biological weapons 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 Zoonoses so:Ebola virus disease