Noroviruses are a genetically diverse group of single stranded RNA, non enveloped 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:
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 five different genogroups (GI, GII, GIII, GIV, and GV), which can be further divided into different genetic clusters or genotypes. 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 reports have shown a link between blood group and susceptibility to infection by norovirus.
A 2008 study suggests that the protein MDA-5 may be the primary immune sensor that detects the presence of noroviruses in the body.
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).
Noroviruses contain a positive-sense 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.
Posted in: NOROVIRUS CLASSIFICATION
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