Editing Norovirus (section)

== Epidemiology ==
[[File:Reports by Month of Norovirus.svg|class=skin-invert-image|thumb|300px|Annual Trend in Reports of Norovirus Infection in England and Wales (2000–2011). Source: HPA]]
[[File:Norovirus Cases per Year.png|class=skin-invert-image|thumb|300px|Laboratory reports of norovirus infections in England and Wales 2000–2012. Source: HPA, NB Testing methods changed in 2007.<ref>{{cite news|url=https://www.telegraph.co.uk/health/healthnews/9698039/Winter-vomiting-bug-cases-up-40-per-cent-Health-Protection-Agency.html|archive-url=https://web.archive.org/web/20121124173337/http://www.telegraph.co.uk/health/healthnews/9698039/Winter-vomiting-bug-cases-up-40-per-cent-Health-Protection-Agency.html|url-status=dead|archive-date=November 24, 2012|title=Winter vomiting bug cases up 40 percent: Health Protection Agency|date=24 November 2012|work=Telegraph.co.uk|access-date=21 February 2016|last1=Smith|first1=Rebecca | name-list-style = vanc }}</ref>]]

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.<ref name=FERG>{{cite journal |vauthors=Ahmed SM, Hall AJ, Robinson AE, etal |title=Global prevalence of norovirus in cases of gastroenteritis: a systematic review and meta-analysis |journal=Lancet Infect Dis |volume=14 |issue=8 |pages=725–30 |date=August 2014 |pmid=24981041 |doi=10.1016/S1473-3099(14)70767-4 |pmc=8006533 |url=https://zenodo.org/record/1260252 |access-date=2019-06-24 |archive-date=2020-04-03 |archive-url=https://web.archive.org/web/20200403224838/https://zenodo.org/record/1260252 |url-status=live }}</ref>

Age and emergence of new norovirus strains do not appear to affect the proportion of gastroenteritis attributable to norovirus.<ref name=FERG/>

In the United States, the estimated annual number of norovirus cases {{As of|2023|pre=in|bare=yes}} was 21 million,<ref>{{Citation |last=Capece |first=Gregory |title=Norovirus |date=2024 |work=StatPearls |url=http://www.ncbi.nlm.nih.gov/books/NBK513265/ |access-date=2024-08-04 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=30020637 |last2=Gignac |first2=Elizabeth}}</ref> representing a rate of 6,270 cases per 100,000 individuals.

Norovirus is a common cause of epidemics of gastroenteritis on [[cruise ship]]s. The CDC, through its Vessel Sanitation Program, records and investigates outbreaks of gastrointestinal illness&nbsp;– mostly caused by norovirus&nbsp;– on cruise ships with both a US and foreign itinerary;<ref name=CDC>{{cite web | author=CDC VSP | url=https://www.cdc.gov/nceh/vsp/surv/gilist.htm | title=Vessel Sanitation Program – Outbreak Updates for International Cruise Ships | publisher=Centers for Disease Control and Prevention | access-date=9 May 2016 | archive-date=10 May 2016 | archive-url=https://web.archive.org/web/20160510060625/http://www.cdc.gov/nceh/vsp/surv/gilist.htm | url-status=live }}</ref> there were 12 in 2015, and 10 from 1&nbsp;January to 9&nbsp;May 2016. An outbreak may affect over 25% of passengers, and a smaller proportion of crew members.<ref>{{cite web |url=https://www.cdc.gov/nceh/vsp/surv/outbreak/2016/april16_balmoral.htm |title=CDC – Vessel Sanitation Program – Balmoral, April 16, 2016 |website=Cdc.gov |access-date=9 May 2016 |archive-date=14 May 2016 |archive-url=https://web.archive.org/web/20160514100616/http://www.cdc.gov/nceh/vsp/surv/outbreak/2016/april16_balmoral.htm |url-status=live }}</ref>