Norwalk virus group
Encyclopedia
Norovirus is an RNA virus
(taxonomic
family
Caliciviridae
) that causes approximately 90% of epidemic
non-bacterial outbreaks of gastroenteritis
around the world, and may be responsible for 50% of all foodborne outbreak
s of gastroenteritis in the US. Norovirus affects people of all ages. The viruses are transmitted by fecally
contaminated food or water, by person-to-person contact, and via aerosolization of the virus and subsequent contamination of surfaces.
After infection
, immunity
to norovirus is usually incomplete and temporary. There is an inherited
predisposition to infection, and individuals with blood type O
are more often infected, while blood types B and AB can confer partial protection against symptomatic infection.
Outbreaks of norovirus infection often occur in closed or semi-closed communities, such as long-term care facilities, overnight camps, hospitals, prisons, dormitories, and cruise ships where the infection spreads very rapidly either by person-to-person transmission or through contaminated food. Many norovirus outbreaks have been traced to food that was handled by one infected person.
Norovirus is rapidly inactivated by either sufficient heating or by chlorine-based disinfectants, but the virus is less susceptible to alcohol
s and detergent
s as it does not have a lipid
envelope
.
(PCR) assay
s or real-time PCR
assays, which give results within a few hours. These assays are very sensitive and can detect concentrations as low as 10 virus particles.
Tests such as ELISA
that use antibodies
against a mixture of norovirus strains are available commercially but lack specificity and sensitivity.
As said previously Norovirus is extremely infectious. In one outbreak at an international scout jamboree 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 average ill person still infected 2.1 other people. A CDC
study of eleven 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
and salad
ingredients are the foods most often implicated in norovirus outbreaks. Ingestion of shellfish that have not been sufficiently heated poses a high risk for norovirus infection. Foods other than shellfish may be contaminated by infected food handlers.
Noroviruses (NoV) are a genetically diverse group of single stranded RNA, nonenveloped viruses belonging to the Caliciviridae
family. According to the International Committee on Taxonomy of Virus, the genus
Norovirus has one species, which is called "Norwalk virus" and assigned the abbreviation "NV". Serotypes, strains and isolates include:
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.
Noroviruses can genetically be classified into 5 different genogroups (GI, GII, GIII, GIV, and GV), which can be further divided into different genetic clusters or genotype
s. For example genogroup II, the most prevalent human genogroup, presently contains 19 genotypes. Genogroups I, II and IV infect humans, whereas genogroup III infects bovine species
and genogroup V has recently been isolated in mice.
Most noroviruses that infect humans belong to genogroup 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-90s, Farmington Hills virus associated with outbreaks in Europe
and the United States
in 2002 and in 2004 Hunter virus was associated with outbreaks in Europe
, Japan
and Australasia
. In 2006 there was another large increase in NoV infection around the globe. Two new GII.4 variants caused around 80% of those Norovirus associated outbreaks and they have been termed 2006a and 2006b. Recent reports have shown a link between the expression of human histo-blood group antigens (HBGAs) and the susceptibility to norovirus infection.
Studies have suggested that the viral capsid of noroviruses may have evolved from selective pressure of human HBGAs.
A 2008 study suggests that the protein MDA-5
may be the primary immune sensor that detects the presence of noroviruses in the body. Interestingly, some people have common variations of the MDA-5 gene that could make them more susceptible to norovirus infection.
A 2010 study suggested that a specific genetic version of Norovirus (which would not be distinguishable from other types of the virus using standard viral antibody tests) interacts with a specific mutation in the ATG16L1
gene to help trigger symptomatic Crohn's Disease
in mice that have been subjected to a chemical that causes intestinal injury similar to the process in humans (there are other similar ways for such diseases to happen like this, and this study in itself does not prove that Norovirus causes Crohn's in humans).
RNA
genome
of approximately 7.5 kbp, encoding a major structural protein
(VP1) of about 58~60 kDa
and a minor capsid
protein (VP2). The virus particles demonstrate an amorphous surface structure when visualized using electron microscopy and are between 27-38 nm in size.
The most variable region of the viral capsid is the P2 domain,which contains antigen-presenting sites and carbohydrate-receptor binding regions.
. After approximately 1 to 2 days, norovirus symptoms can appear. The principal symptom is acute gastroenteritis
that develops between 24 and 48 hours after exposure, and lasts for 24–60 hours. The disease is usually self-limiting
, and characterized by nausea
, forceful vomiting, watery diarrhea
, and abdominal pain; and in some cases, loss of taste. General lethargy, weakness, muscle aches, headache, coughs, and low-grade fever may occur.
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 US is estimated to be around 300 each year, with most of these occurring in the very young, elderly, and persons with weakened immune systems. Symptoms may become life-threatening in these groups if dehydration
is ignored or not treated.
is an effective method to reduce the spread of norovirus pathogen
s. Sanitizing of surfaces where the norovirus may be present is recommended. Alcohol rubs are not very effective at dealing with Norovirus as it does not have a lipid
viral envelope
.
In health-care environments, the prevention of nosocomial infection
s involves routine and terminal cleaning
. Nonflammable alcohol vapor in CO2 systems are used in health care environments where medical electronics would be adversely affected by aerosolized chlorine or other caustic compounds.
Ligocyte announced in 2007 that it was working on a vaccine and had started phase 1 trials. As of 2011, a monovalent nasal vaccine has completed phase I/II trials, while bivalent intramuscular and nasal vaccines are at earlier stages of development.
) are being employed by governmental laboratories such as the FDA in the USA. However, routine methods to detect the virus on other food items are not readily available because of the variable nature of different food items affecting concentration and extraction of the virus and presence of factors that make PCR (polymerase chain reaction) analysis techniques ineffective.
In Guangdong province of China, The Provincial Health Department said, on December 17, 2010, it has confirmed 429 cases of norovirus infection in the November outbreak in Conghua of Guangzhou, but no one died from it.
, USA, where an outbreak of acute gastroenteritis
occurred among children at Bronson Elementary School in November 1968. The name was shortened to norovirus after being identified in a number of outbreaks on cruise ships and receiving attention throughout the USA. 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
and sequencing
of the Norwalk virus genome showed that these viruses have a genomic organization consistent with viruses belonging to the family Caliciviridae
. The name norovirus (Norovirus for the genus) was approved by the International Committee on Taxonomy of Viruses
in 2002.
Common names of the illness caused by noroviruses are winter vomiting disease, viral gastroenteritis
, and acute non-bacterial gastroenteritis, also colloquially known as "stomach flu"—a broad name that refers to gastric inflammation caused by a range of viruses and bacteria.
The virus has previously been called Norwalk virus, Norwalk-like virus, SRSVs (Small Round Structured Viruses), and Snow Mountain virus.
RNA virus
An RNA virus is a virus that has RNA as its genetic material. This nucleic acid is usually single-stranded RNA but may be double-stranded RNA...
(taxonomic
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Caliciviridae
Caliciviridae
The Caliciviridae family are a family of viruses, members of Class IV of the Baltimore scheme. They are positive-sense, single stranded RNA which is non-segmented. The caliciviruses have been found in a number of organisms such as humans, cattle, pigs, cats, chickens, reptiles, dolphins and...
) that causes approximately 90% of epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...
non-bacterial outbreaks of gastroenteritis
Gastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
around the world, and may be responsible for 50% of all foodborne outbreak
Outbreak
Outbreak is a term used in epidemiology to describe an occurrence of disease greater than would otherwise be expected at a particular time and place. It may affect a small and localized group or impact upon thousands of people across an entire continent. Two linked cases of a rare infectious...
s of gastroenteritis in the US. Norovirus affects people of all ages. The viruses are transmitted by fecally
Fecal-oral route
The fecal-oral route, or alternatively, the oral-fecal route or orofecal route is a route of transmission of diseases, in which they are passed when pathogens in fecal particles from one host are introduced into the oral cavity of another potential host.There are usually intermediate steps,...
contaminated food or water, by person-to-person contact, and via aerosolization of the virus and subsequent contamination of surfaces.
After infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
, immunity
Immunity (medical)
Immunity is a biological term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non-specific components. The non-specific components act either as barriers or as eliminators of wide...
to norovirus is usually incomplete and temporary. There is an inherited
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
predisposition to infection, and individuals with blood type O
Blood type
A blood type is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells . These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system...
are more often infected, while blood types B and AB can confer partial protection against symptomatic infection.
Outbreaks of norovirus infection often occur in closed or semi-closed communities, such as long-term care facilities, overnight camps, hospitals, prisons, dormitories, and cruise ships where the infection spreads very rapidly either by person-to-person transmission or through contaminated food. Many norovirus outbreaks have been traced to food that was handled by one infected person.
Norovirus is rapidly inactivated by either sufficient heating or by chlorine-based disinfectants, but the virus is less susceptible to alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s and detergent
Detergent
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...
s as it does not have a lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
envelope
Viral envelope
Many viruses have viral envelopes covering their protein capsids. The envelopes typically are derived from portions of the host cell membranes , but include some viral glycoproteins. Functionally, viral envelopes are used to help viruses enter host cells...
.
Diagnosis
Specific diagnosis of norovirus is routinely made by polymerase chain reactionPolymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
(PCR) assay
Assay
An assay is a procedure in molecular biology for testing or measuring the activity of a drug or biochemical in an organism or organic sample. A quantitative assay may also measure the amount of a substance in a sample. Bioassays and immunoassays are among the many varieties of specialized...
s or real-time PCR
Real-time polymerase chain reaction
In molecular biology, real-time polymerase chain reaction, also called quantitative real time polymerase chain reaction or kinetic polymerase chain reaction , is a laboratory technique based on the PCR, which is used to amplify and simultaneously quantify a targeted DNA molecule...
assays, which give results within a few hours. These assays are very sensitive and can detect concentrations as low as 10 virus particles.
Tests such as ELISA
ELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
that use antibodies
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
against a mixture of norovirus strains are available commercially but lack specificity and sensitivity.
Transmission
Noroviruses are transmitted directly from person to person and indirectly via contaminated water and food. They are highly contagious, with as few as one to ten virus particles being able to cause infection. Transmission occurs through ingesting contaminated food and water and by person-to-person spread. Transmission through fecal-oral can be aerosolized when those stricken with the illness vomit and can be aerosolized 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 after symptoms have subsided and shedding can still be detected many weeks after infection.As said previously Norovirus is extremely infectious. In one outbreak at an international scout jamboree 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 average ill person still infected 2.1 other people. A CDC
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
study of eleven outbreaks in New York State
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
lists the suspected mode of transmission
Transmission (medicine)
In medicine and biology, transmission is the passing of a communicable disease from an infected host individual or group to a conspecific individual or group, regardless of whether the other individual was previously infected...
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
Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...
and salad
Salad
Salad is any of a wide variety of dishes, including vegetable salads; salads of pasta, legumes, eggs, or grains; mixed salads incorporating meat, poultry, or seafood; and fruit salads. They may include a mixture of cold and hot, often including raw vegetables or fruits.Green salads include leaf...
ingredients are the foods most often implicated in norovirus outbreaks. Ingestion of shellfish that have not been sufficiently heated poses a high risk for norovirus infection. Foods other than shellfish may be contaminated by infected food handlers.
Classification
Caliciviridae
The Caliciviridae family are a family of viruses, members of Class IV of the Baltimore scheme. They are positive-sense, single stranded RNA which is non-segmented. The caliciviruses have been found in a number of organisms such as humans, cattle, pigs, cats, chickens, reptiles, dolphins and...
family. According to the International Committee on Taxonomy of Virus, the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Norovirus has one species, which is called "Norwalk virus" and assigned the abbreviation "NV". Serotypes, strains and isolates include:
- Norwalk virus [M87661] (Hu/NLV/NV/1968/US)
- Hawaii virus [U07611] (Hu/NLV/HV/1971/US)
- Snow Mountain virus [L23831] (Hu/NLV/SMV/1976/US)
- Mexico virus [U22498] (Hu/NLV/MX/1989/MX)
- Desert Shield virus [U04469] (Hu/NLV/DSV395/1990/SR)
- Southampton virus [L07418] (Hu/NLV/SHV/1991/UK)
- Lordsdale virus [X86557] (Hu/NLV/LD/1993/UK)
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.
Noroviruses can genetically be classified into 5 different genogroups (GI, GII, GIII, GIV, and GV), which can be further divided into different genetic clusters or genotype
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...
s. For example genogroup II, the most prevalent human genogroup, presently contains 19 genotypes. Genogroups I, II and IV infect humans, whereas genogroup III infects bovine species
Bovinae
The biological subfamily Bovinae includes a diverse group of 10 genera of medium to large sized ungulates, including domestic cattle, the bison, African buffalo, the water buffalo, the yak, and the four-horned and spiral-horned antelopes...
and genogroup V has recently been isolated in mice.
Most noroviruses that infect humans belong to genogroup GI and GII.
Noroviruses from Genogroup II, genotype 4 (abbreviated as GII.4) account for the majority of adult outbreaks of gastroenteritis
Gastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
and often sweep across the globe.
Recent examples include US95/96-US strain, associated with global outbreaks in the mid- to late-90s, Farmington Hills virus associated with outbreaks in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
in 2002 and in 2004 Hunter virus was associated with outbreaks in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Australasia
Australasia
Australasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...
. In 2006 there was another large increase in NoV infection around the globe. Two new GII.4 variants caused around 80% of those Norovirus associated outbreaks and they have been termed 2006a and 2006b. Recent reports have shown a link between the expression of human histo-blood group antigens (HBGAs) and the susceptibility to norovirus infection.
Studies have suggested that the viral capsid of noroviruses may have evolved from selective pressure of human HBGAs.
A 2008 study suggests that the protein MDA-5
IFIH1
Interferon-induced helicase C domain-containing protein 1, also known as MDA5 , is an enzyme that in humans is encoded by the IFIH1 gene...
may be the primary immune sensor that detects the presence of noroviruses in the body. Interestingly, some people have common variations of the MDA-5 gene that could make them more susceptible to norovirus infection.
A 2010 study suggested that a specific genetic version of Norovirus (which would not be distinguishable from other types of the virus using standard viral antibody tests) interacts with a specific mutation in the ATG16L1
ATG16L1
Autophagy-related protein 16-1 is a protein that in humans is encoded by the ATG16L1 gene.-Function:Autophagy is the major intracellular degradation system delivering cytoplasmic components to lysosomes, and it accounts for degradation of most long-lived proteins and some organelles...
gene to help trigger symptomatic Crohn's Disease
Crohn's disease
Crohn's disease, also known as regional enteritis, is a type of inflammatory bowel disease that may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms...
in mice that have been subjected to a chemical that causes intestinal injury similar to the process in humans (there are other similar ways for such diseases to happen like this, and this study in itself does not prove that Norovirus causes Crohn's in humans).
Structure
Noroviruses contain a positive-senseSense (molecular biology)
In molecular biology and genetics, sense is a concept used to compare the polarity of nucleic acid molecules, such as DNA or RNA, to other nucleic acid molecules...
RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
of approximately 7.5 kbp, encoding a major structural protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
(VP1) of about 58~60 kDa
KDA
KDA may refer to:* Karachi Development Authority* Kongsberg Defence & Aerospace* Kotelawala Defence Academy* Kramer Design Associates* Lithium diisopropylamide, KDA is the potassium analogue of lithium diisopropylamideOr kDa may refer to:...
and a minor capsid
Capsid
A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...
protein (VP2). The virus particles demonstrate an amorphous surface structure when visualized using electron microscopy and are between 27-38 nm in size.
The most variable region of the viral capsid is the P2 domain,which contains antigen-presenting sites and carbohydrate-receptor binding regions.
Pathophysiology
When a person becomes infected with norovirus, the virus begins to multiply within the small intestineSmall intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
. After approximately 1 to 2 days, norovirus symptoms can appear. The principal symptom is acute gastroenteritis
Gastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
that develops between 24 and 48 hours after exposure, and lasts for 24–60 hours. The disease is usually self-limiting
Self-limiting (biology)
In biology, a self-limiting organism or colony of organisms limits its own growth by its actions. For example, a single organism may have a maximum size determined by genetics, or a colony of organisms may release waste which is ultimately toxic to the colony once it exceeds a certain population...
, and characterized by nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
, forceful vomiting, watery diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
, and abdominal pain; and in some cases, loss of taste. General lethargy, weakness, muscle aches, headache, coughs, and low-grade fever may occur.
Severe illness is rare: although people are frequently treated at the emergency ward, they are rarely admitted to the hospital
Hospital
A hospital is a health care institution providing patient treatment by specialized staff and equipment. Hospitals often, but not always, provide for inpatient care or longer-term patient stays....
. The number of deaths from norovirus in the US is estimated to be around 300 each year, with most of these occurring in the very young, elderly, and persons with weakened immune systems. Symptoms may become life-threatening in these groups if dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
is ignored or not treated.
Prevention
Hand washingHand washing
Hand washing for hand hygiene is the act of cleaning the hands with or without the use of water or another liquid, or with the use of soap, for the purpose of removing soil, dirt, and/or microorganisms....
is an effective method to reduce the spread of norovirus pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
s. Sanitizing of surfaces where the norovirus may be present is recommended. Alcohol rubs are not very effective at dealing with Norovirus as it does not have a lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
viral envelope
Viral envelope
Many viruses have viral envelopes covering their protein capsids. The envelopes typically are derived from portions of the host cell membranes , but include some viral glycoproteins. Functionally, viral envelopes are used to help viruses enter host cells...
.
In health-care environments, the prevention of nosocomial infection
Nosocomial infection
A nosocomial infection , also known as a hospital-acquired infection or HAI, is an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff...
s involves routine and terminal cleaning
Terminal cleaning
Terminal Cleaning describes a cleaning method used in healthcare environments to control the spread of infections.- Justification :Nosocomial infections claim approximately 90,000 lives in the United States annually...
. Nonflammable alcohol vapor in CO2 systems are used in health care environments where medical electronics would be adversely affected by aerosolized chlorine or other caustic compounds.
Ligocyte announced in 2007 that it was working on a vaccine and had started phase 1 trials. As of 2011, a monovalent nasal vaccine has completed phase I/II trials, while bivalent intramuscular and nasal vaccines are at earlier stages of development.
Detection in foods
Routine protocols to detect norovirus (norovirus RNA) in clams and oysters by RT-PCR (reverse transcription polymerase chain reactionReverse transcription polymerase chain reaction
Reverse transcription polymerase chain reaction is a variant of polymerase chain reaction , a laboratory technique commonly used in molecular biology to generate many copies of a DNA sequence, a process termed "amplification"...
) are being employed by governmental laboratories such as the FDA in the USA. However, routine methods to detect the virus on other food items are not readily available because of the variable nature of different food items affecting concentration and extraction of the virus and presence of factors that make PCR (polymerase chain reaction) analysis techniques ineffective.
Epidemiology
Epidemiological data from developing countries about the importance of norovirus in pediatric diarrhea is limited. Recently, in Nicaragua, it has been observed that norovirus is responsible for 11% of the diarrhea cases occurring in children <5 years of age at community level and 15% of the moderate to severe cases requiring intravenous re-hydration.In Guangdong province of China, The Provincial Health Department said, on December 17, 2010, it has confirmed 429 cases of norovirus infection in the November outbreak in Conghua of Guangzhou, but no one died from it.
History
The norovirus was originally named the Norwalk agent after Norwalk, OhioNorwalk, Ohio
At the 2000 census, there were 16,238 people, 6,377 households and 4,234 families residing in the city. The population density was 1,950.3 per square mile . There were 6,687 housing units at an average density of 803.1 per square mile...
, USA, where an outbreak of acute gastroenteritis
Gastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
occurred among children at Bronson Elementary School in November 1968. The name was shortened to norovirus after being identified in a number of outbreaks on cruise ships and receiving attention throughout the USA. In 1972, electron microscopy on stored human stool
Human feces
Human feces , also known as a stool, is the waste product of the human digestive system including bacteria. It varies significantly in appearance, according to the state of the digestive system, diet and general health....
samples identified a virus, which was given the name Norwalk virus. Numerous outbreaks with similar symptoms have been reported since. The cloning
Cloning
Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...
and sequencing
Sequencing
In genetics and biochemistry, sequencing means to determine the primary structure of an unbranched biopolymer...
of the Norwalk virus genome showed that these viruses have a genomic organization consistent with viruses belonging to the family Caliciviridae
Caliciviridae
The Caliciviridae family are a family of viruses, members of Class IV of the Baltimore scheme. They are positive-sense, single stranded RNA which is non-segmented. The caliciviruses have been found in a number of organisms such as humans, cattle, pigs, cats, chickens, reptiles, dolphins and...
. The name norovirus (Norovirus for the genus) was approved by the International Committee on Taxonomy of Viruses
International Committee on Taxonomy of Viruses
The International Committee on Taxonomy of Viruses is a committee which authorizes and organizes the taxonomic classification of viruses. They have developed a universal taxonomic scheme for viruses and aim to describe all the viruses of living organisms. Members of the committee are considered to...
in 2002.
Common names of the illness caused by noroviruses are winter vomiting disease, viral gastroenteritis
Gastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
, and acute non-bacterial gastroenteritis, also colloquially known as "stomach flu"—a broad name that refers to gastric inflammation caused by a range of viruses and bacteria.
The virus has previously been called Norwalk virus, Norwalk-like virus, SRSVs (Small Round Structured Viruses), and Snow Mountain virus.
External links
- NHS Choices Health A-Z Norovirus infections
- 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
- Winter Vomiting Disease – UK government factsheet
- The latest news and research on Norovirus
- Virus Pathogen Database and Analysis Resource (ViPR): Caliciviridae