Balancing Public Health and Industry Health: Norovirus and Shellfish in the UK

Jul 9, 2013 | Alexandra Thomsen | Research & Policy

Norovirus is the most common stomach bug in the United Kingdom, affecting between 600,000 and 1 million people in the UK each year. Also known as the “winter vomiting bug” or “stomach flu” (despite having no relation to influenza), norovirus is a major cause of acute gastroenteritis marked by nausea, stomach pain, diarrhea, and vomiting. This highly contagious virus is often transmitted through contact with contaminated surfaces, infected individuals, and contaminated food and drink. The source of infection currently causing debate is shellfish, specifically bivalve mollusks - such as oysters and mussels - that accumulate potentially harmful bacteria and viruses in their tissues when they filter-feed in sewage-contaminated waters. Concern over norovirus infection in shellfish - particularly in oysters, which are often consumed raw - rose in late 2011 after the UK’s Food Standards Agency reported that 76% of UK oysters contain the virus.

Mussel producers in the United Kingdom have recently expressed concern, as reported in the UK’s Daily Post, that efforts by the European Food Safety Authority (EFSA) to reduce norovirus contamination in shellfish will damage their industry. While environmental surveys and E. coli contamination assessments are already in place, the EFSA issued a further recommendation in January 2012 that shellfish only be produced in waters not contaminated by norovirus, which would put many shellfish farmers out of business. The EFSA also recommends establishing a limit for norovirus presence in harvests because current methods to remove the virus from shellfish (heat treatment, immersion in tanks of clean seawater - known as “depuration”- and relocation from contaminated to clean areas - known as “relaying”) have not been effective.

Although it seems intuitive to support these proposed EFSA regulations because their goal is to protect consumers, many shellfish producers oppose them because production would be shut down in many locations where waters are already contaminated with norovirus. One mussel producer tells the Daily Post’s Owen Hughes: “This industry is worth £200m a year in the UK and employs 2,000 people,” many of whom could lose their jobs following new norovirus regulations.

While shellfish are a known source of norovirus infection in humans, shellfish producers argue that more stringent regulations will not make a significant difference in the spread of the virus: norovirus is already highly prevalent in the UK and other EU countries, and individuals are far more likely to become infected by other people than by contact with shellfish. In addition, the amount of norovirus contamination in shellfish is likely the same as it was decades ago—the only difference now is that the EFSA can quantify and report it.

Shellfish farmers have offered several compelling reasons as to why the proposed EFSA norovirus regulations should not be implemented, yet the main question seems to be whether it is more important to protect the industry (which, by spreading norovirus, may be doing more harm than good) or to protect consumers (though it is unclear how much of an impact new regulations would actually have on the spread of the virus).

Unfortunately, there is no specific treatment for norovirus. The CDC recommends drinking fluids to prevent dehydration from vomiting and diarrhea. Norovirus is a pretty resilient virus: it can remain in stool for up to two weeks after a person feels better, and it can survive temperatures as high as 140 degrees Fahrenheit. To prevent norovirus, the CDC recommends frequent handwashing, thorough cooking of foods, and disinfection of surface areas and clothes that may be contaminated with the vomit or stool of someone with the virus.




EFSA assesses control options for norovirus in oysters.


Investigation into the prevalence, distribution and levels of norovirus titre in oyster harvesting areas in the UK. - .UdrHnz75k8Y



'Norovirus tests are the worst thing we face': Warning from mussel industry.

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