Eating raw oysters can carry a risk of food poisoning because shellfish can contain harmful bacteria and viruses because of the way they feed. Oysters filter large volumes of water to get their food and any bacteria and viruses that may be in the water can build up within the oyster.
Controls before and after commercial harvesting provide good protection against harmful bacteria, but it can be difficult to remove viruses from live shellfish. Thorough cooking will destroy these viruses but many shellfish are eaten raw or only lightly cooked so may still contain viruses when eaten. The FSA and the shellfish industry are continuing to work together to improve methods for removing viruses from live shellfish.
Infections linked to norovirus tend to be more common during the winter. This time last year there appeared to be an increase in the number of people, in the UK, with norovirus infections linked to eating raw oysters.
Dr Paul Cook from the FSA’s Hygiene and Microbiology Division said: ‘We sometimes see an increase in the number of people who get ill with norovirus from eating raw oysters at this time of year. Usually these outbreaks are not linked to any one particular source.
‘Last winter, when the increase in cases was identified, the Agency wrote to food businesses supplying oysters and local authorities with oyster processing plants in their areas advising them to take additional measures to minimise the risk from norovirus where possible.
‘We are reiterating this advice again and also reminding consumers of the possible risk from norovirus infections, which is associated with eating raw oysters.’