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Norovirus found in three quarters of UK oysters

Food Standards Agency warns of food poisoning risk from eating raw oysters

Ingrid Torjesen

Tuesday, 29 November 2011

Three quarters of oysters grown in beds off the UK coastline contain norovirus, research by the Food Standards Agency has found.

The researchers said it was difficult to estimate the potential impact on health. Although the virus was detected at only low levels in 52% of the positive samples, a safe limit for norovirus has not been established and research techniques are not able to differentiate between infectious and non-infectious norovirus material within the oysters.

Between 2009 and 2011, scientists from the Centre for Environment, Fisheries and Aquaculture Science (Cefas), on behalf of the Food Standards Agency, took samples from 39 oyster harvesting areas across the UK. More than 800 samples of 10 oysters each were tested.

David Lees, the lead investigator at Cefas, 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.”

Andrew Wadge, chief scientist at the Food Standards Agency, 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.”

Oysters are traditionally eaten raw, but he said that people should be aware of the risks involved in eating them in this way.

Re-laying is a purification process used to treat bivalve shellfish. Shellfish are harvested from a contaminated area and moved to clean areas, where they are placed on the ocean floor or into containers laid on the ocean floor, or suspended in racks. Re-laying will generally be for at least two months.

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