Three quarters of British-grown oysters contain norovirus, according to research.
A study by the Food Standards Agency (FSA) found that 76 per cent of oysters tested from UK oyster growing beds contained the virus, often called the “winter vomiting bug.”
The virus was detected at “low levels” in more than half of the positive samples, the Agency said. However, according to Dr Andrew Wadge, chief scientist at the FSA, the latest findings have not identified a new food safety risk.
Norovirus is highly infectious, and is the most common viral cause of diarrhoea and vomiting in the UK, according to recent research. The virus is behind outbreaks of vomiting, especially during the winter months.
Most norovirus infections are thought to spread from person-to-person, but it can also be caused by eating contaminated food, including shellfish. Healthy people usually make a full recovery within two to three days.
In the study, scientists from the Centre for Environment, Fisheries and Aquaculture Science (CEFA) took samples from 39 oyster harvesting areas across the UK, and tested more than 800 samples of 10 oysters each.
The FSA said it was difficult to assess the potential threat to health of the findings, as the current testing methods cannot distinguish between infectious and non-infectious norovirus material within the oysters. In addition, scientists have not established whether there is a safe level for norovirus in oysters.
Dr 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.
“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.”