Editing Norovirus (section)

=== 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>