People are sick in the United Kingdom and Hong Kong after eating oysters contaminated with norovirus.

Reports suggest at least 100 people are ill in the UK with 12 cases in Hong Kong from raw oysters produced by Whitstable Oyster Company in the UK.

Specialists from Public Health England (PHE), the Food Standards Agency (FSA) and environmental health teams in Thanet and Canterbury in England are investigating reports of people falling ill with vomiting and diarrhea after eating oysters in late May and early June.

“We are supporting PHE and the local authorities’ investigations into an outbreak of suspected norovirus and we are reiterating our advice to consumers that they should be aware of the risks of eating raw oysters. Elderly people, pregnant women, very young children and people who have a weakened immune system should avoid eating raw or lightly cooked shellfish to reduce their risk of getting food poisoning,” said an FSA statement.

The oyster bed and affected batches have been identified, supplied businesses have been informed and testing is ongoing.

Whitstable Oyster Company has ceased harvesting, no further oysters have been distributed since illnesses occurred, and those distributed before the firm was aware of the outbreak have been withdrawn from the market. All oysters sent for sale are now past their shelf life so there is no known further risk to consumers.

Risk factors for shellfish-related norovirus include cold weather leading to low water temperatures, high prevalence of norovirus in the community, and high rainfall potentially leading to sewage system overflows.

Situation in Hong Kong
The Centre for Food Safety (CFS) of the Food and Environmental Hygiene Department in Hong Kong told traders to suspend the import of raw oysters produced by the company and restaurants to stop selling the products concerned.

A spokesman said regardless of the season or region in which oysters are harvested, consuming them, particularly raw or partially cooked, carries a food safety risk.

“The CFS was notified by the Centre for Health Protection of the Department of Health of several food poisoning cases which involved consumption of raw oysters at one restaurant in Sha Tin and one restaurant in Causeway Bay,” he said.

“The CFS conducted investigations at the restaurants concerned and found that both restaurants had sold raw oysters from the Whitstable Oyster Company in the UK supplied by the same local supplier. As well, the CFS received a notification from the Food Standards Agency that raw oysters supplied by Whitstable Oyster Company were suspected to be contaminated with norovirus.”

Two males and one female, aged 28 to 30, developed abdominal pain, diarrhea, fever and vomiting about 18 to 26 hours after having dinner at a restaurant in Sha Tin on June 26. Another two males and one female, aged 30 to 40, also fell ill about 32 to 34 hours after having lunch at this restaurant on the same day. Five people sought medical advice and one required hospitalization but has since been discharged.

Two males and one female, aged 20 to 22, developed symptoms about 22 to 32 hours after having dinner at a restaurant in Causeway Bay on June 28. Another three females, aged 24 to 25, had similar symptoms about 34 to 43 hours after eating at the same restaurant on June 26. Five of them sought medical advice and none required hospitalization.

Norovirus can contaminate food and water and can also spread through contact with the feces or vomit of an infected person. Although symptoms can be unpleasant, it is considered a mild infection because it is usually short-lived and most people get better without medical treatment.