Editing Norovirus (section)

== Virology ==
{{Virusbox
| name = ''Norovirus''
| image = Norovirus 4.jpg
| image_alt = Transmission electron micrograph of Norovirus particles in feces
| image_caption = [[Transmission electron micrograph]] of ''Norovirus'' particles in feces
| parent = Norovirus
| species = Norovirus norwalkense
| synonyms = * Norwalk virus
| synonyms_ref = <ref name=ictvhistory >{{cite web|title=History of the taxon: Species: ''Norovirus norwalkense'' (2024 Release, MSL #40)|url=https://ictv.global/taxonomy/taxondetails?taxnode_id=202402806&taxon_name=Norovirus%20norwalkense|publisher=International Committee on Taxonomy of Viruses|access-date=20 March 2025}}</ref>
| subdivision_ranks =
| subdivision =
}}

=== Transmission ===
Noroviruses are transmitted directly from person to person (62–84% of all reported outbreaks)<ref>{{cite journal |vauthors=Moore MD, Goulter RM, Jaykus L | title = Human Norovirus as a Foodborne Pathogen: Challenges and Developments | journal = Annual Review of Food Science and Technology  | volume = 6 | issue = 1 | pages = 411–33 | date = April 2015 | doi = 10.1146/annurev-food-022814-015643 |pmid= 25884284| doi-access = free }}</ref> 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.<ref>{{cite web|url=https://www.newscientist.com/article/mg16722551.000-ive-lost-my-appetite.html|title=I've lost my appetite...|author=Robert Matthews|work=New Scientist|access-date=21 February 2016|archive-date=3 May 2015|archive-url=https://web.archive.org/web/20150503052554/http://www.newscientist.com/article/mg16722551.000-ive-lost-my-appetite.html|url-status=live}}</ref> The viruses continue to be [[Viral shedding|shed]] after symptoms have subsided, and shedding can still be detected many weeks after infection.<ref>{{cite journal |vauthors= Atmar RL, Opekun AR, Gilger MA, Estes MK, Crawford SE, Neill FH, Graham DY | title = Norwalk Virus Shedding after Experimental Human Infection | journal = Emerg. Infect. Dis. | volume = 14 | issue = 10 | pages = 1553–7 | date = October 2008 | pmid = 18826818 | pmc = 2609865 | doi = 10.3201/eid1410.080117 |name-list-style=vanc  }}</ref>

Vomiting, in particular, transmits infection effectively and appears to allow [[airborne transmission]]. 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.<ref>{{cite journal |vauthors=Marks PJ, Vipond IB, Carlisle D, Deakin D, Fey RE, Caul EO | title = Evidence for airborne transmission of Norwalk-like virus (NLV) in a hotel restaurant | journal = Epidemiol. Infect. | volume = 124 | issue = 3 | pages = 481–487 | date = June 2000 | pmid = 10982072 | pmc = 2810934 | doi = 10.1017/s0950268899003805 | citeseerx = 10.1.1.404.2721 }}</ref> 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.<ref>{{cite journal |vauthors=Marks PJ, Vipond IB, Regan FM, Wedgwood K, Fey RE, Caul EO | title = A school outbreak of Norwalk-like virus: evidence for airborne transmission | journal = Epidemiol. Infect. | volume = 131 | issue = 1 | pages = 727–736 | date = August 2003 | pmid = 12948373 | pmc = 2870014 | doi = 10.1017/s0950268803008689 }}</ref>

In one outbreak at an international scout [[Jamboree (Scouting)|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 ill person still infected an average of 2.1 other people.<ref>{{cite journal |vauthors= Heijne JC, Teunis P, Morroy G, Wijkmans C, Oostveen S, Duizer E, Kretzschmar M, Wallinga J | title = Enhanced Hygiene Measures and Norovirus Transmission during an Outbreak | journal = Emerg. Infect. Dis. | volume = 15 | issue = 1 | pages = 24–30 | year = 2009 | pmid = 19116045 | pmc = 2660689 | doi = 10.3201/eid1501.080299 }}</ref> A US [[Centers for Disease Control and Prevention]] (CDC) study of 11 outbreaks in New York State lists the suspected [[Transmission (medicine)|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.<ref name="pmid8395330">{{cite journal |vauthors= Hedberg CW, Osterholm MT | title = Outbreaks of food-borne and waterborne viral gastroenteritis | journal = Clin. Microbiol. Rev. | volume = 6 | issue = 3 | pages = 199–210 | year = 1993 | pmid = 8395330 | pmc = 358282 | doi = 10.1128/CMR.6.3.199 }}</ref>

[[Shellfish]] and salad ingredients are the foods most often implicated in norovirus outbreaks. Ingestion of shellfish that has not been sufficiently heated{{spnd}}under {{convert|75|C}}{{spnd}}poses a high risk for norovirus infection.<ref>{{cite web |url=https://www.canada.ca/en/health-canada/services/general-food-safety-tips/safe-internal-cooking-temperatures-chart.html |title=Safe Internal Cooking Temperatures Chart |date=7 May 2015 |publisher=Government of Canada |access-date=27 December 2017 |archive-date=27 December 2017 |archive-url=https://web.archive.org/web/20171227122625/https://www.canada.ca/en/health-canada/services/general-food-safety-tips/safe-internal-cooking-temperatures-chart.html |url-status=live }}</ref><ref>{{cite web|url=http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Norovirus/oysterconsumptionnorovirus/|archive-url=http://webarchive.nationalarchives.gov.uk/20140714084352/http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Norovirus/oysterconsumptionnorovirus/|url-status=dead|archive-date=14 July 2014|title= HPA: Shellfish consumption and the risk of norovirus infection|access-date=21 February 2016}}</ref> Foods other than shellfish may be contaminated by infected food handlers.<ref name="pmid11479930">{{cite journal | vauthors = Parashar UD, Monroe SS | title = 'Norwalk-like viruses' as a cause of foodborne disease outbreaks | journal = Rev. Med. Virol. | volume = 11 | issue = 4 | pages = 243–52 | year = 2001 | pmid = 11479930 | doi = 10.1002/rmv.321 | s2cid = 9922865 | url = https://zenodo.org/record/1229350 | access-date = 2020-09-05 | archive-date = 2020-10-31 | archive-url = https://web.archive.org/web/20201031083507/https://zenodo.org/record/1229350 | url-status = live }}</ref> Many norovirus outbreaks have been traced to food that was handled by only one infected person.<ref name="pmid14672828">{{cite journal |vauthors= Koopmans M, Duizer E | title = Foodborne viruses: an emerging problem | journal = Int. J. Food Microbiol. | volume = 90 | issue = 1 | pages = 23–41 | year = 2004 | pmid = 14672828 | doi = 10.1016/S0168-1605(03)00169-7 | pmc = 7127053 }}</ref>

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.<ref>{{cite web |last1= Sherwood |first1= Dave |title= How a Chilean raspberry scam dodged food safety controls from China to Canada |url= https://www.reuters.com/article/chile-crime-raspberries-insight/how-a-chilean-raspberry-scam-dodged-food-safety-controls-from-china-to-canada-idUSKBN26R1M1 |website= Reuters |access-date= 10 October 2020 |archive-url= https://web.archive.org/web/20201010080047/https://www.reuters.com/article/chile-crime-raspberries-insight/how-a-chilean-raspberry-scam-dodged-food-safety-controls-from-china-to-canada-idUSKBN26R1M1 |archive-date= 10 October 2020 |url-status= dead }}</ref>

According to the CDC, there was a surge in norovirus cases on thirteen [[cruise ship|cruise ships]] in 2023, which marks the highest number of outbreaks since 2012.<ref>{{cite web |title=Cruise ships are seeing the highest number of norovirus outbreaks in a decade |url=https://www.deseret.com/2023/7/13/23793778/highest-number-of-norovirus-outbreaks-on-cruise-ships |access-date=15 July 2023 |website=Deseret News|date=13 July 2023 }}</ref>

=== Classification ===
Noroviruses (NoV) are a genetically diverse group of single-stranded [[positive-sense RNA]], non-[[virus envelope|enveloped]] viruses belonging to the family ''[[Caliciviridae]]''.<ref name=ICTV>{{Cite web|url=http://www.ictv.global/report/caliciviridae|title=Family: Caliciviridae &#124; ICTV|website=www.ictv.global|access-date=2019-10-02|archive-date=2021-08-29|archive-url=https://web.archive.org/web/20210829153617/https://talk.ictvonline.org/ictv-reports/ictv_online_report/positive-sense-rna-viruses/w/caliciviridae|url-status=live}}</ref><ref name=health>{{cite web |last1=Public Health Laboratory Network |title=Norovirus Laboratory Case Definition (LCD) |url=http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-phlncd-norwalk.htm |publisher=Australian Government Department of Health and Ageing |language=en |date=25 September 2006 |access-date=15 September 2020 |archive-date=1 May 2008 |archive-url=https://web.archive.org/web/20080501230732/http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-phlncd-norwalk.htm |url-status=live }}</ref> According to the [[International Committee on Taxonomy of Viruses]], the genus ''Norovirus'' has one species: Norwalk virus (''Norovirus norwalkense'').<ref name=ICTV/><ref name=ictvhistory />

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]]s.<ref>{{cite journal |last1=Atmar |first1=Robert L |last2=Baehner |first2=Frank |last3=Cramer |first3=Jakob P |last4=Lloyd |first4=Eric |last5=Sherwood |first5=James |last6=Borkowski |first6=Astrid |last7=Mendelman |first7=Paul M |last8=Al-Ibrahim |first8=Mohamed S |last9=Bernstein |first9=David L |last10=Brandon |first10=Donald M |last11=Chu |first11=Laurence |last12=Davis |first12=Matthew G |last13=Epstein |first13=Robert J |last14=Frey |first14=Sharon E |last15=Rosen |first15=Jeffrey B |last16=Treanor |first16=John J |title=Persistence of Antibodies to 2 Virus-Like Particle Norovirus Vaccine Candidate Formulations in Healthy Adults: 1-Year Follow-up With Memory Probe Vaccination |journal=The Journal of Infectious Diseases |date=15 August 2019 |volume=220 |issue=4 |pages=603–614 |doi=10.1093/infdis/jiz170|pmid=31001633 }}</ref>

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.<ref name=health/>

Most noroviruses that infect humans belong to genogroups GI and GII.<ref name="pmid10752550">{{cite journal | vauthors = Vinjé J, Green J, Lewis DC, Gallimore CI, Brown DW, Koopmans MP | title = Genetic polymorphism across regions of the three open reading frames of "Norwalk-like viruses" | journal = Arch. Virol. | volume = 145 | issue = 2 | pages = 223–41 | year = 2000 | pmid = 10752550 | doi = 10.1007/s007050050020 | s2cid = 20525287 }}</ref>
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.<ref>{{cite journal |vauthors=Noel JS, Fankhauser RL, Ando T, Monroe SS, Glass RI | title = Identification of a distinct common strain of "Norwalk-like viruses" having a global distribution | journal = J. Infect. Dis. | volume = 179 | issue = 6 | pages = 1334–44 | year = 2000 | pmid = 10228052 | doi = 10.1086/314783 | doi-access = free }}</ref>

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.<ref name="pmid18177226">{{cite journal |vauthors=Tu ET, Bull RA, Greening GE, Hewitt J, Lyon MJ, Marshall JA, McIver CJ, Rawlinson WD, White PA | title = Epidemics of gastroenteritis during 2006 were associated with the spread of norovirus GII.4 variants 2006a and 2006b | journal = Clin. Infect. Dis. | volume = 46 | issue = 3 | pages = 413–20 | year = 2008 | pmid = 18177226 | doi = 10.1086/525259 | s2cid = 27972379 | doi-access =  }}</ref> Reports have shown a link between the expression of human histo-[[blood group antigen]]s (HBGAs) and the susceptibility to norovirus infection. Studies have suggested the [[capsid]] of noroviruses may have evolved from [[selective pressure]] of human HBGAs.<ref name="pmid21519121">{{cite journal | author = Shirato H | title = Norovirus and histo-blood group antigens | journal = Japanese Journal of Infectious Diseases | volume = 64 | issue = 2 | pages = 95–103 | year = 2011 | doi = 10.7883/yoken.64.95 | pmid = 21519121 | doi-access = free }}</ref> HBGAs are not, however, the receptor or facilitator of norovirus infection. Co-factors such as [[bile salts]] may facilitate the infection, making it more intense when introduced during or after the initial infection of the host tissue.<ref name=":0">{{Cite journal|last1=Graziano|first1=Vincent R.|last2=Wei|first2=Jin|last3=Wilen|first3=Craig B.|date=30 May 2019|title=Norovirus Attachment and Entry|journal=Viruses|language=en|volume=11|issue=6|pages=495|doi=10.3390/v11060495|pmid=31151248|pmc=6630345|doi-access=free}}</ref> Bile salts are produced by the liver in response to eating fatty foods, and they help with the absorption of consumed [[lipid|lipids]]. It is not yet clear at what specific point in the Norovirus replication cycle bile salts facilitate infection: penetration, uncoating, or maintaining capsid stability.<ref name=":0" />

The protein [[IFIH1|MDA-5]] may be the primary immune sensor that detects the presence of noroviruses in the body.<ref>{{cite journal | vauthors = McCartney SA, Thackray LB, Gitlin L, Gilfillan S, Virgin HW, Virgin Iv HW, Colonna M | title = MDA-5 Recognition of a Murine Norovirus | journal = PLOS Pathog | volume = 4 | issue = 7 | page = e1000108 | date = July 18, 2008 | pmid = 18636103 | pmc = 2443291 | doi = 10.1371/journal.ppat.1000108 | veditors = Baric RS | doi-access = free }}</ref>  Some people have common variations of the MDA-5 gene that could make them more susceptible to norovirus infection.<ref>[http://newswise.com/articles/view/542714/ Researchers Discover Primary Sensor That Detects Stomach Viruses] {{Webarchive|url=https://web.archive.org/web/20090202094714/http://newswise.com/articles/view/542714/ |date=2009-02-02 }} Newswise, Retrieved on July 20, 2008.</ref>

=== Structure ===
[[File:Norwalk Caspid.jpg|thumb|X-ray crystallographic structure of the Norwalk virus capsid]]

{| class="wikitable" style="text-align:center"
|-
! Genus !! Structure || Symmetry !! Capsid !! Genomic arrangement !! Genomic segmentation
|-
|Norovirus||Icosahedral||T=1, T=3||Non-enveloped||Linear||Monopartite
|}

Viruses in Norovirus are non-enveloped, with [[icosahedral]] geometries. [[Capsid]] diameters vary widely, from 23 to 40&nbsp;[[Meter#SI prefixed forms of metre|nm]] in diameter. The larger capsids (38–40&nbsp;nm) exhibit [[Capsid#Triangulation number|T=3 symmetry]] and are composed of 180 [[Major capsid protein VP1|VP1 proteins]]. Small capsids (23&nbsp;nm) show T=1 symmetry, and are composed of 60 VP1 proteins.<ref name=ViralZone>{{cite web|title=Viral Zone|url=http://viralzone.expasy.org/all_by_species/194.html|publisher=ExPASy|access-date=15 June 2015|archive-date=9 January 2017|archive-url=https://web.archive.org/web/20170109200451/http://viralzone.expasy.org/all_by_species/194.html|url-status=live}}</ref> The virus particles demonstrate an amorphous surface structure when visualized using [[electron microscopy]].<ref name="pmid11444031">{{cite book |vauthors=Prasad BV, Crawford S, Lawton JA, Pesavento J, Hardy M, Estes MK | title = Gastroenteritis Viruses | chapter = Structural Studies on Gastroenteritis Viruses | volume = 238 | pages = 26–37; discussion 37–46 | year = 2001 | pmid = 11444031 | doi = 10.1002/0470846534.ch3 | isbn = 978-0-470-84653-7 | series = Novartis Foundation Symposia }}</ref>

===Genome===

Noroviruses contain a linear, non-segmented,<ref name=ViralZone /> [[Sense (molecular biology)|positive-sense]] [[RNA]] [[genome]] of approximately 7.5 [[Megabases|kilobases]], encoding a large polyprotein which is cleaved into six smaller non-structural proteins (NS1/2 to NS7)<ref>{{cite journal | vauthors = Thorne LG, Goodfellow IG | title = Norovirus gene expression and replication | journal = The Journal of General Virology | volume = 95 | issue = Pt 2 | pages = 278–91 | date = February 2014 | pmid = 24243731 | doi = 10.1099/vir.0.059634-0 | doi-access = free }}</ref> by the viral [[3C-like protease]] (NS6), a major structural protein ([[Major capsid protein VP1|VP1]]) of about 58~60 [[kDa]] and a minor capsid protein ([[Minor capsid protein VP2|VP2]]).<ref name="pmid10804143">{{cite journal | vauthors = Clarke IN, Lambden PR | title = Organization and expression of calicivirus genes | journal = The Journal of Infectious Diseases | volume = 181 | pages = S309-16 | date = May 2000 | issue = Suppl 2 | pmid = 10804143 | doi = 10.1086/315575 | doi-access = free }}</ref>

The most variable region of the viral capsid is the P2 [[Domain (protein)|domain]], which contains [[Antigen presentation|antigen-presenting]] sites and carbohydrate-receptor binding regions.<ref>{{cite journal |vauthors=Tan M, Hegde RS, Jiang X | title = The P Domain of Norovirus Capsid Protein Forms Dimer and Binds to Histo-Blood Group Antigen Receptors | journal = J. Virol. | volume = 78 | issue = 12 | pages = 6233–42 | year = 2004 | pmid = 15163716 | pmc = 416535 | doi = 10.1128/JVI.78.12.6233-6242.2004 }}</ref><ref>{{cite journal |vauthors=Tan M, Huang P, Meller J, Zhong W, Farkas T, Jiang X |title=Mutations within the P2 domain of norovirus capsid affect binding to human histo-blood group antigens: evidence for a binding pocket |journal=J. Virol. |volume=77 |issue=23 |pages=12562–71 |year=2003 |pmid=14610179 |pmc=262557 |doi=10.1128/jvi.77.23.12562-12571.2003}} {{cite journal|title=Erratum |journal=J. Virol.  |volume=78 |issue=6 |page=3200 |year=2004|doi=10.1128/JVI.78.6.3201.2004 |author=Tan M|citeseerx=10.1.1.212.5257|s2cid=220476008 }}</ref><ref>{{cite journal |vauthors=Cao S, Lou Z, Tan M, Chen Y, Liu Y, Zhang Z, Zhang XC, Jiang X, Li X, Rao Z | title = Structural Basis for the Recognition of Blood Group Trisaccharides by Norovirus | journal = J. Virol. | volume = 81 | issue = 11 | pages = 5949–57 | year = 2007 | pmid = 17392366 | pmc = 1900264 | doi = 10.1128/JVI.00219-07 }}</ref><ref>{{cite journal | vauthors = Lundborg M, Ali E, Widmalm G | title = An ''in silico'' virtual screening study for the design of norovirus inhibitors: fragment-based molecular docking and binding free energy calculations | journal = Carbohydr. Res. | volume = 378 | pages = 133–8 | year = 2013 | pmid = 23582100 | doi = 10.1016/j.carres.2013.03.012 | s2cid = 9941188 | url = https://su.diva-portal.org/smash/get/diva2:656620/FULLTEXT01.pdf | archive-url = https://web.archive.org/web/20210829153644/https://su.diva-portal.org/smash/get/diva2:656620/FULLTEXT01.pdf |access-date = 2019-06-24 | archive-date = 2021-08-29 |url-status=live }}</ref><ref>{{cite journal |vauthors=Ali ES, Rajapaksha H, Jillian MC, Petrovsky N | title = Norovirus drug candidates that inhibit viral capsid attachment to human histo-blood group antigens | journal = Antiviral Res. | volume = 133 | pages = 14–22 | year = 2016 | pmid = 27421712 | doi = 10.1016/j.antiviral.2016.07.006 | pmc=5026924}}</ref>

===Evolution===

Groups 1, 2, 3, and 4 last shared a [[common ancestor]] in AD 867.<ref name=Kobayashi2016>{{cite journal |doi=10.1038/srep29400 |title=Molecular evolution of the capsid gene in human norovirus genogroup II |year=2016 |last1=Kobayashi |first1=Miho |last2=Matsushima |first2=Yuki |last3=Motoya |first3=Takumi |last4=Sakon |first4=Naomi |last5=Shigemoto |first5=Naoki |last6=Okamoto-Nakagawa |first6=Reiko |last7=Nishimura |first7=Koichi |last8=Yamashita |first8=Yasutaka |last9=Kuroda |first9=Makoto |last10=Saruki |first10=Nobuhiro |last11=Ryo |first11=Akihide |last12=Saraya |first12=Takeshi |last13=Morita |first13=Yukio |last14=Shirabe |first14=Komei |last15=Ishikawa |first15=Mariko |last16=Takahashi |first16=Tomoko |last17=Shinomiya |first17=Hiroto |last18=Okabe |first18=Nobuhiko |last19=Nagasawa |first19=Koo |last20=Suzuki |first20=Yoshiyuki |last21=Katayama |first21=Kazuhiko |last22=Kimura |first22=Hirokazu |journal=Scientific Reports |volume=6 |page=29400 |pmid=27384324 |pmc=4935990 |bibcode=2016NatSR...629400K }}</ref> The group 2 and group 4 viruses last shared a common ancestor in approximately AD 1443 (95% highest posterior density AD 1336–1542).<ref name=Ozaki2018>{{cite journal | doi=10.3389/fmicb.2018.03070 | doi-access=free | title=Molecular Evolutionary Analyses of the RNA-Dependent RNA Polymerase Region in Norovirus Genogroup II | year=2018 | last1=Ozaki | first1=Keita | last2=Matsushima | first2=Yuki | last3=Nagasawa | first3=Koo | last4=Motoya | first4=Takumi | last5=Ryo | first5=Akihide | last6=Kuroda | first6=Makoto | last7=Katayama | first7=Kazuhiko | last8=Kimura | first8=Hirokazu | journal=Frontiers in Microbiology | volume=9 | page=3070 | pmid=30619155 | pmc=6305289 }}</ref> Several estimates of the evolution rate have been made varying from 8.98 × 10<sup>−3</sup> to 2.03 × 10<sup>−3</sup> substitutions per site per year.{{cn|date=August 2022}}

The estimated [[mutation rate]] (1.21{{e|−2}} to 1.41 {{e|−2}} substitutions per site per year) in this virus is high even compared with other RNA viruses.<ref name=Victoria2009>{{cite journal |vauthors=Victoria M, Miagostovich MP, Ferreira MS, Vieira CB, Fioretti JM, Leite JP, Colina R, Cristina J | title = Bayesian coalescent inference reveals high evolutionary rates and expansion of Norovirus populations | journal = Infect Genet Evol | volume = 9 | issue = 5 | pages = 927–932 | year = 2009 | pmid = 19559104 | doi = 10.1016/j.meegid.2009.06.014 | doi-access = free | bibcode = 2009InfGE...9..927V }}</ref>

In addition, a [[recombination hotspot]] exists at the ORF1-ORF2 (VP1) junction.<ref>{{cite journal | vauthors = Tsimpidis M, Bachoumis G, Mimouli K, Kyriakopoulou Z, Robertson DL, Markoulatos P, Amoutzias GD | title = T-RECs: rapid and large-scale detection of recombination events among different evolutionary lineages of viral genomes | journal = BMC Bioinformatics | volume = 18 | issue = 1 | pages = 13 | date = January 2017 | pmid = 28056784 | pmc = 5216575 | doi = 10.1186/s12859-016-1420-z | doi-access = free }}</ref>

===Replication cycle===
[[Viral replication]] is cytoplasmic. Entry into the host cell is achieved by attachment to host receptors, which mediates [[endocytosis]]. Positive-stranded RNA virus [[RNA transcription|transcription]] 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.<ref name=ViralZone />

{| class="wikitable sortable" style="text-align:center"
|-
! Genus !! Host details !! Tissue tropism !! Entry details !! Release details !! Replication site !! Assembly site !! Transmission
|-
|Norovirus||Humans; mammals||Intestinal epithelium||Cell receptor endocytosis||Lysis||Cytoplasm||Cytoplasm||Oral-fecal
|}