Norovirus, also known as Norwalk virus and sometimes referred to as the winter vomiting disease, is the most common cause of

gastroenteritis Gastroenteritis, also known as infectious diarrhea, is an inflammation of the Human gastrointestinal tract, gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of ...

. Infection is characterized by non-bloody

diarrhea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

vomiting Vomiting (also known as emesis, puking and throwing up) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteritis, pre ...

, and stomach pain. Fever or headaches may also occur. Symptoms usually develop 12 to 48 hours after being exposed, and recovery typically occurs within one to three days. Complications are uncommon, but may include

dehydration In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild deh ...

, especially in the young, the old, and those with other health problems. The

virus A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...

is usually spread by the

fecal–oral route The fecal–oral route (also called the oral–fecal route or orofecal route) describes a particular route of transmission of a disease wherein pathogens in fecal particles pass from one person to the mouth of another person. Main causes of fec ...

. This may be through contaminated food or water or person-to-person contact. It may also spread via contaminated surfaces or through

air An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

from the vomit of an infected person. Risk factors include unsanitary food preparation and sharing close quarters. Diagnosis is generally based on symptoms. Confirmatory testing is not usually available but may be performed by public health agencies during outbreaks. Prevention involves proper

hand washing Hand washing (or handwashing), also known as hand hygiene, is the act of cleaning one's hands with soap, soap or handwash and water to remove viruses, bacteria, microorganisms, dirt, grease, and other harmful or unwanted substances stuck to th ...

and

disinfection 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 ...

of contaminated surfaces. There is no

vaccine A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifi ...

or specific treatment for norovirus. Management involves

supportive care Symptomatic treatment, supportive care, supportive therapy, or palliative treatment is any medical therapy of a disease that only affects its symptoms, not the underlying cause. It is usually aimed at reducing the signs and symptoms for the co ...

such as drinking sufficient fluids or

intravenous fluids Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...

Oral rehydration solutions Oral rehydration therapy (ORT) also officially known as Oral Rehydration Solution is a type of fluid replacement used to prevent and treat dehydration, especially due to diarrhea. It involves drinking water with modest amounts of sugar and salt ...

are the preferred fluids to drink, although other drinks without

caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class and is the most commonly consumed Psychoactive drug, psychoactive substance globally. It is mainly used for its eugeroic (wakefulness pr ...

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

can help. Hand sanitizers based on

alcohols In chemistry, an alcohol (), is a type of organic compound that carries at least one hydroxyl () functional group bound to a Saturated and unsaturated compounds, saturated carbon atom. Alcohols range from the simple, like methanol and ethanol ...

tend to be ineffective against noroviruses due to their being non-enveloped, although some virus genotypes are more susceptible. Norovirus results in about 685 million cases of disease and 200,000 deaths globally a year. It is common both in the developed and

developing world A developing country is a sovereign state with a less-developed industrial base and a lower Human Development Index (HDI) relative to developed countries. However, this definition is not universally agreed upon. There is also no clear agreeme ...

. Those under the age of five are most often affected, and in this group it results in about 50,000 deaths in the developing world. Norovirus infections occur more commonly during winter months. It often occurs in

outbreaks In epidemiology, an outbreak is a sudden increase in occurrences of a disease when cases are in excess of normal expectancy for the location or season. It may affect a small and localized group or impact upon thousands of people across an entire ...

, especially among those living in close quarters. In the United States, it is the cause of about half of all

foodborne disease Foodborne illness (also known as foodborne disease and food poisoning) is any illness resulting from the food contaminant, contamination of food by pathogenic bacteria, viruses, or parasites, as well as prions (the agents of mad cow disease), a ...

outbreaks. The virus is named after the city of

Norwalk, Ohio Norwalk is a city in Huron County, Ohio, United States, and its county seat. The population was 17,068 at the 2020 census. The city is the center of the Norwalk micropolitan area and part of the Cleveland–Akron–Canton combined statistical ...

, in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, where an outbreak occurred in 1968.

Signs and symptoms

Norovirus infection is characterized by

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat. Over 30 d ...

, watery

, abdominal pain, and in some cases, loss of taste. A person usually develops symptoms of

12 to 48 hours after being exposed to norovirus. General lethargy, weakness, muscle aches, headaches, and low-grade fevers may occur. The disease is usually self-limiting, and severe illness is rare. Although having norovirus can be unpleasant, it is not usually dangerous, and most who contract it make a full recovery within two to three days. Norovirus can establish a long-term infection in people who are

immunocompromised Immunodeficiency, also known as immunocompromise, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that affe ...

, such as those with

common variable immunodeficiency Common variable immunodeficiency (CVID) is an inborn immune disorder characterized by recurrent infections and low antibody levels, specifically in immunoglobulin (Ig) types IgG, IgM, and IgA. Symptoms generally include high susceptibility to ...

or with a suppressed immune system after

organ transplantation Organ transplantation is a medical procedure in which an organ is removed from one body and placed in the body of a recipient, to replace a damaged or missing organ. The donor and recipient may be at the same location, or organs may be trans ...

. These infections can be with or without symptoms. In severe cases, persistent infections can lead to norovirus‐associated

enteropathy Enteropathy refers to any pathology of the intestine. Although enteritis specifically refers to an inflammation of the intestine, and is thus a more specific term than "enteropathy", the two terms are sometimes used interchangeably. __TOC__ Types ...

, intestinal villous atrophy, and

malabsorption Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal (GI) tract. Impairment can be of single or multiple nutrients depending on the abnormality. This may lead to malnutrition and a varie ...

Virology

Transmission

Noroviruses are transmitted directly from person to person (62–84% of all reported outbreaks) and indirectly via contaminated water and food. Transmission can be aerosolized when those stricken with the illness vomit or by a toilet flush when vomit or diarrhea is present; infection can follow eating food or breathing air near an episode of vomiting, even if cleaned up. The viruses continue to be

shed A shed is typically a simple, single-storey (though some sheds may have two or more stories and or a loft) roofed structure, often used for storage, for hobby, hobbies, or as a workshop, and typically serving as outbuilding, such as in a bac ...

after symptoms have subsided, and shedding can still be detected many weeks after infection. Vomiting, in particular, transmits infection effectively and appears to allow

airborne transmission Airborne transmission or aerosol transmission is transmission of an infectious disease through small particles suspended in the air. Infectious diseases capable of airborne transmission include many of considerable importance both in human a ...

. In one incident, a person who vomited spread the infection across a restaurant, suggesting that many unexplained cases of food poisoning may have their source in vomit. In December 1998, 126 people were dining at six tables; one person vomited onto the floor. Staff quickly cleaned up, and people continued eating. Three days later others started falling ill; 52 people reported a range of symptoms, from fever and nausea to vomiting and diarrhea. The cause was not immediately identified. Researchers plotted the seating arrangement: more than 90% of the people at the same table as the sick person later reported becoming ill. There was a direct correlation between the risk of infection of people at other tables and how close they were to the sick person. More than 70% of the diners at an adjacent table fell ill; at a table on the other side of the restaurant, the infection rate was still 25%. The outbreak was attributed to a Norwalk-like virus (norovirus). Other cases of transmission by vomit were later identified. In one outbreak at an international scout

jamboree In Scouting, a jamboree is a large gathering of Scouts and/or Girl Guides who rally at a national or international level. History The 1st World Scout Jamboree was held in 1920, and was hosted by the United Kingdom. Since then, there have been t ...

in the Netherlands, each person with gastroenteritis infected an average of 14 people before increased hygiene measures were put in place. Even after these new measures were enacted, an ill person still infected an average of 2.1 other people. A US

Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the National public health institutes, national public health agency of the United States. It is a Federal agencies of the United States, United States federal agency under the United S ...

(CDC) study of 11 outbreaks in New York State lists the suspected mode of transmission as person-to-person in seven outbreaks, foodborne in two, waterborne in one, and one unknown. The source of waterborne outbreaks may include water from municipal supplies, wells, recreational lakes, swimming pools, and ice machines.

Shellfish Shellfish, in colloquial and fisheries usage, are exoskeleton-bearing Aquatic animal, aquatic invertebrates used as Human food, food, including various species of Mollusca, molluscs, crustaceans, and echinoderms. Although most kinds of shellfish ...

and salad ingredients are the foods most often implicated in norovirus outbreaks. Ingestion of shellfish that has not been sufficiently heatedunder poses a high risk for norovirus infection. Foods other than shellfish may be contaminated by infected food handlers. Many norovirus outbreaks have been traced to food that was handled by only one infected person. From March and August 2017, in Quebec, Canada, there was an outbreak of norovirus that sickened more than 700 people. According to an investigation by Canada's CFIA Food Control Agency, the culprit was frozen raspberries imported from Harbin Gaotai Food Co Ltd, a Chinese supplier. Canadian authorities subsequently issued a recall on raspberry products from Harbin Gaotai. According to the CDC, there was a surge in norovirus cases on thirteen

cruise ships Cruise ships are large passenger ships used mainly for vacationing. Unlike ocean liners, which are used for transport, cruise ships typically embark on round-trip voyages to various ports of call, where passengers may go on tours known as " ...

in 2023, which marks the highest number of outbreaks since 2012.

Classification

Noroviruses (NoV) are a genetically diverse group of single-stranded positive-sense RNA, non- enveloped viruses belonging to the family ''

Caliciviridae The ''Caliciviridae'' are a family of "small round structured" viruses, members of Class IV of the Baltimore scheme. Caliciviridae bear resemblance to enlarged picornavirus and was formerly a separate genus within the picornaviridae. They are ...

''. According to the

International Committee on Taxonomy of Viruses The International Committee on Taxonomy of Viruses (ICTV) authorizes and organizes the taxonomic classification of and the nomenclature for viruses. The ICTV develops a universal taxonomic scheme for viruses, and thus has the means to appropri ...

, the genus ''Norovirus'' has one species: Norwalk virus (''Norovirus norwalkense''). Noroviruses can genetically be classified into at least seven different genogroups (GI, GII, GIII, GIV, GV, GVI, and GVII), which can be further divided into other genetic clusters or

genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...

s. Noroviruses commonly isolated in cases of acute gastroenteritis belong to two genogroups: genogroup I (GI) includes Norwalk virus, Desert Shield virus, and Southampton virus; and II (GII), which includes Bristol virus, Lordsdale virus, Toronto virus, Mexico virus, Hawaii virus and Snow Mountain virus. Most noroviruses that infect humans belong to genogroups GI and GII. Noroviruses from genogroup II, genotype 4 (abbreviated as GII.4) account for the majority of adult outbreaks of gastroenteritis and often sweep across the globe. Recent examples include US95/96-US strain, associated with global outbreaks in the mid- to late-1990s; Farmington Hills virus associated with outbreaks in Europe and the United States in 2002 and in 2004; and Hunter virus which was associated with outbreaks in Europe, Japan, and Australasia. In 2006, there was another large increase in NoV infection around the globe. Reports have shown a link between the expression of human histo-

blood group antigen A blood type (also known as a blood group) is based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrates, glycoproteins, or glycoli ...

s (HBGAs) and the susceptibility to norovirus infection. Studies have suggested the

capsid 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 m ...

of noroviruses may have evolved from

selective pressure Evolutionary pressure, selective pressure or selection pressure is exerted by factors that reduce or increase reproductive success in a portion of a population, driving natural selection. It is a quantitative description of the amount of change oc ...

of human HBGAs. HBGAs are not, however, the receptor or facilitator of norovirus infection. Co-factors such as

bile salts Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. Diverse bile acids are synthesized in the liver in peroxisomes. Bile acids are conjugated with taurine or glycine residues to give anions called bile ...

may facilitate the infection, making it more intense when introduced during or after the initial infection of the host tissue. Bile salts are produced by the liver in response to eating fatty foods, and they help with the absorption of consumed

lipids Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins Vitamin A, A, Vitamin D, D, Vitamin E, E and Vitamin K, K), monoglycerides, diglycerides, phospholipids, and others. The fu ...

. It is not yet clear at what specific point in the Norovirus replication cycle bile salts facilitate infection: penetration, uncoating, or maintaining capsid stability. The protein MDA-5 may be the primary immune sensor that detects the presence of noroviruses in the body. Some people have common variations of the MDA-5 gene that could make them more susceptible to norovirus infection.

Structure

Viruses in Norovirus are non-enveloped, with

icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrical tha ...

geometries.

Capsid 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 m ...

diameters vary widely, from 23 to 40 nm in diameter. The larger capsids (38–40 nm) exhibit T=3 symmetry and are composed of 180 VP1 proteins. Small capsids (23 nm) show T=1 symmetry, and are composed of 60 VP1 proteins. The virus particles demonstrate an amorphous surface structure when visualized using

electron microscopy An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing i ...

Genome

Noroviruses contain a linear, non-segmented,

positive-sense In molecular biology and genetics, the sense of a nucleic acid molecule, particularly of a strand of DNA or RNA, refers to the nature of the roles of the strand and its complement in specifying a sequence of amino acids. Depending on the context, ...

RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

of approximately 7.5 kilobases, encoding a large polyprotein which is cleaved into six smaller non-structural proteins (NS1/2 to NS7) by the viral 3C-like protease (NS6), a major structural protein ( VP1) of about 58~60

kDa The dalton or unified atomic mass unit (symbols: Da or u, respectively) is a unit of mass defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest. It is a non-SI unit accepted f ...

and a minor capsid protein ( VP2). The most variable region of the viral capsid is the P2

domain A domain is a geographic area controlled by a single person or organization. Domain may also refer to: Law and human geography * Demesne, in English common law and other Medieval European contexts, lands directly managed by their holder rather ...

, which contains antigen-presenting sites and carbohydrate-receptor binding regions.

Evolution

Groups 1, 2, 3, and 4 last shared a

common ancestor Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. According to modern evolutionary biology, all living beings could be descendants of a unique ancestor commonl ...

in AD 867. The group 2 and group 4 viruses last shared a common ancestor in approximately AD 1443 (95% highest posterior density AD 1336–1542). Several estimates of the evolution rate have been made varying from 8.98 × 10⁻³ to 2.03 × 10⁻³ substitutions per site per year. The estimated

mutation rate In genetics, the mutation rate is the frequency of new mutations in a single gene, nucleotide sequence, or organism over time. Mutation rates are not constant and are not limited to a single type of mutation; there are many different types of mu ...

(1.21 to 1.41 substitutions per site per year) in this virus is high even compared with other RNA viruses. In addition, a

recombination hotspot Recombination hotspots are regions in a genome that exhibit elevated rates of recombination relative to a neutral expectation. The recombination rate within hotspots can be hundreds of times that of the surrounding region. Recombination hotspots r ...

exists at the ORF1-ORF2 (VP1) junction.

Replication cycle

Viral replication Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome ...

is cytoplasmic. Entry into the host cell is achieved by attachment to host receptors, which mediates

endocytosis Endocytosis is a cellular process in which Chemical substance, substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a Vesicle (biology and chem ...

. Positive-stranded RNA virus

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, often th ...

is the method of replication. Translation takes place by leaky scanning and RNA termination-reinitiation. Humans and other mammals serve as the natural host. Transmission routes are fecal-oral and contamination.

Pathophysiology

When a person becomes infected with norovirus, the virus replicates within the

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

. The principal symptom is acute

, characterized by nausea, forceful vomiting, watery

, and abdominal pain, that develops 12 to 48 hours after exposure and lasts for 24–72 hours. Sometimes there is loss of taste, general

lethargy Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness, or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overw ...

, weakness, muscle aches,

headache A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe ...

cough A cough is a sudden expulsion of air through the large breathing passages which can help clear them of fluids, irritants, foreign particles and Microorganism, microbes. As a protective reflex, coughing can be repetitive with the cough reflex fol ...

, and/or low-grade

fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...

. The disease is usually self-limiting. Severe illness is rare; although people are frequently treated at the emergency ward, they are rarely admitted to the hospital. The number of deaths from norovirus in the United States is estimated to be around 570–800 each year, with most of these occurring in the very young, the elderly, and persons with weakened immune systems. Symptoms may become life-threatening in these groups if

electrolyte imbalance Electrolyte imbalance, or water-electrolyte imbalance, is an abnormality in the concentration of electrolytes in the body. Electrolytes play a vital role in maintaining homeostasis in the body. They help to regulate heart and neurological function ...

is ignored or left untreated.

Diagnosis

Specific diagnosis of norovirus is routinely made by

polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to amplify a very small sample of DNA (or a part of it) sufficiently to enable detailed st ...

(PCR) assays or

quantitative PCR A real-time polymerase chain reaction (real-time PCR, or qPCR when used quantitatively) is a laboratory technique of molecular biology based on the polymerase chain reaction (PCR). It monitors the amplification of a targeted DNA molecule duri ...

assays, which give results within a few hours. These assays are very sensitive and can detect as few as 10 virus particles. Tests such as

ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay is a solid-phase type of enzyme immunoassay (EIA) to detect the presence of ...

that use

antibodies An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...

against a mixture of norovirus strains are available commercially, but lack specificity and sensitivity.

Prevention

After

infection An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

immunity Immunity may refer to: Medicine * Immunity (medical), resistance of an organism to infection or disease * ''Immunity'' (journal), a scientific journal published by Cell Press Biology * Immune system Engineering * Radiofrequence immunity ...

to the ''same'' strain of the virus – the genotype – protects against reinfection for six months to two years. This immunity does not fully protect against infection with the other diverse genotypes of the virus. In

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, norovirus is a

notifiable disease A notifiable disease is any disease that is required by law to be reported to government authorities. The collation of information allows the authorities to monitor the disease, and provides early warning of possible outbreaks. In the case of lives ...

. In both the US and the UK it is not notifiable.

Hand washing and disinfectants

Hand washing with soap and water is an effective method for reducing the transmission of norovirus pathogens. Alcohol rubs (≥62%

isopropyl alcohol Isopropyl alcohol (IUPAC name propan-2-ol and also called isopropanol or 2-propanol) is a colorless, flammable, organic compound with a pungent alcoholic odor. Isopropyl alcohol, an organic polar molecule, is miscible in water, ethanol, an ...

) may be used as an adjunct, but are less effective than hand-washing, as norovirus lacks a

lipid Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing ...

viral envelope A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. A viral envelope protein or E protein is a protein in the en ...

. Hand sanitizers based on

tend to be ineffective against noroviruses due to their being non-enveloped, although some virus genotypes were found in ''

in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...

'' tests with

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

and

to be more susceptible. Alcohol susceptibility patterns between different norovirus genotypes were found to vary widely, and virolysis data for a single strain or genotype was not representative for all noroviruses. Another study found that alcohol in combination with acid (1%

citric acid Citric acid is an organic compound with the formula . It is a Transparency and translucency, colorless Weak acid, weak organic acid. It occurs naturally in Citrus, citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, ...

, e.g. from 15% concentrated lemon juice) produced an effective disinfectant of noroviruses. Surfaces where norovirus particles may be present can be sanitised with a solution of 1.5% to 7.5% of household bleach in water, or other disinfectants effective against norovirus.

Health care facilities

In healthcare environments, the prevention of

nosocomial infection A hospital-acquired infection, also known as a nosocomial infection (from the Greek , meaning "hospital"), is an infection that is acquired in a hospital or other healthcare facility. To emphasize both hospital and nonhospital settings, it is s ...

s involves routine and terminal cleaning. Nonflammable alcohol vapor in CO₂ systems is used in health care environments where medical electronics would be adversely affected by aerosolized chlorine or other caustic compounds. In 2011, the CDC published a clinical practice guideline addressing strategies for the prevention and control of norovirus gastroenteritis outbreaks in healthcare settings. Based on a systematic review of published scientific studies, the guideline presents 51 specific

evidence-based Evidence-based practice is the idea that occupational practices ought to be based on scientific evidence. The movement towards evidence-based practices attempts to encourage and, in some instances, require professionals and other decision-makers ...

recommendations, which were organized into 12 categories: 1) patient cohorting and isolation precautions, 2) hand hygiene, 3) patient transfer and ward closure, 4) food handlers in healthcare, 5) diagnostics, 6)

personal protective equipment Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, elect ...

, 7) environmental cleaning, 8) staff leave and policy, 9) visitors, 10) education, 11) active case-finding, and 12) communication and notification. The guideline also identifies eight high-priority recommendations and suggests several areas in need of future research.

Vaccine trials

LigoCyte announced in 2007 that it was working on a vaccine and had started phase 1 trials. The company has since been taken over by

Takeda Pharmaceutical Company The is a Japanese multinational pharmaceutical company. It is the third largest pharmaceutical company in Asia, behind Sinopharm and Shanghai Pharmaceuticals, and one of the top 20 largest pharmaceutical companies in the world by revenue (t ...

. , a bivalent (NoV GI.1/GII.4) intramuscular vaccine had completed phase 1 trials. In 2020 the phase 2b trials were finished. The vaccine relies on using a

virus-like particle Virus-like particles (VLPs) are molecules that closely resemble viruses, but are non-infectious because they contain no viral genetic material. They can be naturally occurring or synthesized through the individual expression of viral structural pro ...

that is made of the norovirus capsid proteins in order to mimic the external structure of the virus. Since there is no RNA in this particle, it is incapable of reproducing and cannot cause an infection.

Persistence

The norovirus can survive for long periods outside a human host depending on the surface and temperature conditions: it can survive for weeks on hard and soft surfaces, and it can survive for months, maybe even years in contaminated still water. A 2006 study found the virus remained on surfaces used for food preparation seven days after contamination.

Detection in food

Routine protocols to detect norovirus in clams and oysters by

reverse transcription polymerase chain reaction Reverse transcription polymerase chain reaction (RT-PCR) is a laboratory technique combining reverse transcription of RNA into DNA (in this context called complementary DNA or cDNA) and amplification of specific DNA targets using polymerase cha ...

are being employed by governmental laboratories such as the

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...

(FDA) in the US.

Treatment

There is no specific medicine to treat people with norovirus illness. Treatments aim to avoid complications by measures such as the

management of dehydration Dehydration can occur as a result of diarrhea, vomiting, water scarcity, physical activity, and alcohol consumption. Management of dehydration (or rehydration) seeks to reverse dehydration by replenishing the lost water and electrolytes. Water and ...

caused by fluid loss in vomiting and diarrhea, and to mitigate symptoms using

antiemetics An antiemetic is a drug that is effective against vomiting and nausea. Antiemetics are typically used to treat motion sickness and the side effects of opioid analgesics, general anaesthetics, and chemotherapy directed against cancer. They may be ...

and antidiarrheals.

Epidemiology

Norovirus causes about 18% of all cases of acute gastroenteritis worldwide. It is relatively common in developed countries and in low-mortality developing countries (20% and 19% respectively) compared to high-mortality developing countries (14%). Proportionately it causes more illness in people in the community or in hospital outpatients (24% and 20% respectively) as compared with hospital inpatients (17%) in whom other causes are more common. Age and emergence of new norovirus strains do not appear to affect the proportion of gastroenteritis attributable to norovirus. In the United States, the estimated annual number of norovirus cases was 21 million, representing a rate of 6,270 cases per 100,000 individuals. Norovirus is a common cause of epidemics of gastroenteritis on

cruise ship Cruise ships are large passenger ships used mainly for vacationing. Unlike ocean liners, which are used for transport, cruise ships typically embark on round-trip voyages to various ports of call, where passengers may go on Tourism, tours k ...

s. The CDC, through its Vessel Sanitation Program, records and investigates outbreaks of gastrointestinal illness – mostly caused by norovirus – on cruise ships with both a US and foreign itinerary; there were 12 in 2015, and 10 from 1 January to 9 May 2016. An outbreak may affect over 25% of passengers, and a smaller proportion of crew members.

Human genetics

Epidemiological studies have shown that individuals with different ABO(H) (histo-

blood group A blood type (also known as a blood group) is based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrates, glycoproteins, or glycoli ...

) phenotypes are infected with NoV strains in a

-specific manner. GII.4 includes global epidemic strains and binds to more histo-blood group antigens than other genogroups.

FUT2 Galactoside 2-alpha-L-fucosyltransferase 2 is an enzyme that in humans is encoded by the ''FUT2'' (fucosyltransferase 2) gene. FUT2 is a key enzyme that catalyzes the transfer of L-fucose from guanosine diphosphate-beta-L-fucose to the terminal ...

fucosyltransferase A fucosyltransferase is an enzyme that transfers an L-fucose sugar from a GDP-fucose (guanosine diphosphate-fucose) donor substrate to an acceptor substrate. The acceptor substrate can be another sugar such as the transfer of a fucose to a core ...

transfers a

fucose Fucose is a hexose deoxy sugar with the chemical formula C6H12O5. It is found on ''N''-linked glycans on the mammalian, insect and plant cell surface. Fucose is the fundamental sub-unit of the seaweed polysaccharide fucoidan. The α(1→3) l ...

sugar to the end of the ABO(H) precursor in gastrointestinal cells and saliva glands. The ABH-antigen produced is thought to act as a receptor for human norovirus: A non-functional

FUT2 provides high protection from the most common norovirus strain, GII.4. Homozygous carriers of any nonsense mutation in the FUT2 gene are called ''

non-secretors Secretor status refers to the presence or absence of water-soluble ABO blood group antigens in a person's bodily fluids, such as saliva, tears, breast milk, urine, and semen. People who secrete these antigens in their bodily fluids are referred to ...

'', as no ABH-antigen is produced. Approximately 20% of Caucasians are non-secretors due to G428A and C571T nonsense mutations in FUT2 and therefore have strong – although not absolute – protection from the norovirus GII.4. Non-secretors can still produce ABH antigens in erythrocytes, as the precursor is formed by FUT1. Some norovirus genotypes (GI.3) can infect non-secretors.

History

The norovirus was originally named the "Norwalk agent" after

, in the United States, where an outbreak of acute gastroenteritis occurred among children at Bronson Elementary School in November 1968. In 1972, electron microscopy on stored human stool samples identified a virus, which was given the name "Norwalk virus". Numerous outbreaks with similar symptoms have been reported since. The

cloning Cloning is the process of producing individual organisms with identical genomes, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction; this reproduction of an organism by itself without ...

and sequencing of the Norwalk virus genome showed that these viruses have a genomic organization consistent with viruses belonging to the family

. The name "norovirus" (''Norovirus'' for the genus) was approved by the

(ICTV) in 2002. In 2011, however, a press release and a newsletter were published by ICTV, which strongly encouraged the media, national health authorities, and the scientific community to use the virus name Norwalk virus, rather than the genus name Norovirus when referring to outbreaks of the disease. This was also a public response by ICTV to the request from an individual in Japan to rename the Norovirus genus because of the possibility of negative associations for people in Japan and elsewhere who have the family name "Noro". Before this position of ICTV was made public, ICTV consulted widely with members of the Caliciviridae Study Group and carefully discussed the case. In addition to "Norwalk agent" and "Norwalk virus", the virus has also been called "Norwalk-like virus", "small, round-structured viruses" (SRSVs), Spencer flu, and "Snow Mountain virus". Common names of the illness caused by noroviruses still in use include "Roskilde illness", "winter vomiting disease", "winter vomiting bug", "viral gastroenteritis", and "acute nonbacterial gastroenteritis".

References

External links

Norovirus (vomiting bug) NHS
Norovirus infections
Global network and database noroviruses

CDC Viral Gastroenteritis FAQs
Center for Disease Control and Prevention of Food Illness Fact Sheet
"Norovirus in Healthcare Facilities Fact Sheet"
CDC, released December 21, 2006
tips from CDC for cruise vacationers

Virus Pathogen Database and Analysis Resource (ViPR): Caliciviridae

3D structure of Norovirus from the EM Data Bank
at the

European Bioinformatics Institute The European Bioinformatics Institute (EMBL-EBI) is an intergovernmental organization (IGO) which, as part of the European Molecular Biology Laboratory (EMBL) family, focuses on research and services in bioinformatics. It is located on the Wel ...

UK
Viralzone: Norovirus

ICTV Report: ''Caliciviridae''
{{Baltimore classification Virus genera Foodborne illnesses Healthcare-associated infections Vomiting Wikipedia medicine articles ready to translate