Norovirus present in three quarters of UK-grown oysters

The Food Standards Agency (FSA) in the UK is warning oysters that have come from British oyster-growing beds are likely to contain norovirus.

It was discovered that the virus – which causes the annual winter vomiting bug and is associated with infectious symptoms such as sickness and diarrhoea – was present in 76 percent of oysters originating from the UK.

In 52 percent of the samples which tested positive for the bug, low levels of the virus were identified.

However, as it is not possible for researchers to differentiate between infectious and non-infectious strains of the virus, the FSA said it does not know what impact these findings will have on public health.

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It now expected that the study’s findings will be referred to and reviewed by European Food Safety Authority.

There are also hopes that this review will be used to advise and encourage the European Commission to set a safety standard regarding levels of the oyster-borne norovirus, of which there is currently none.

The FSA’s Chief Scientist, Andrew Wadge, said: “This research is the first of its kind in the UK. It will be important to help improve the knowledge of the levels of norovirus found in shellfish at production sites.

“The results, along with data from other research, will help us work with producers to find ways to reduce the levels of norovirus in shellfish, and work within Europe to establish safe levels.

Wadge added: “Though oysters are traditionally eaten raw, people should be aware of the risks involved in eating them in this way.

“The Agency advises that older people, pregnant women, very young children and people who are unwell should avoid eating raw or lightly cooked shellfish to reduce their risk of getting food poisoning.”

Over a period of two years, between the years of 2009 and 2011, 39 samples were taken from oyster beds across the UK.

Working on behalf of the FSA, scientists from Cefas (Centre for Environment, Fisheries and Aquaculture Science) then carried out tests on 8,000 oysters – 800 samples of 10 different oysters.

Also commenting on the findings, the Cefas’ lead investigator David Lees, said: “We were fortunate to have excellent cooperation from the oyster producers and from local authority officers in conducting this study.

“Norovirus is a recognised problem for the sector and this study provides important baseline data to help the industry and regulators to focus on the key risks,” he added.

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