Thirteen more people have come down with food poisoning symptoms after consuming raw oysters, bringing the total to 46, the Centre for Health Protection says.

They ate at five different food premises between September 22 and October 11. The latest case was reported to the centre on October 16. None of those affected required hospitalisation.

Raw oysters are a high-risk food. If contaminated and not thoroughly cooked, they can carry norovirus, hepatitis A, or harmful bacteria like vibrio parahaemolyticus.  

Children, the elderly and people with immune deficiency should not eat raw oysters. Thorough cooking can kill viruses and bacteria.

So far this year there have been 87 food poisoning cases reported to the centre caused by norovirus, affecting 349 people who ate contaminated raw or undercooked oysters.

Prevention tips

To prevent food borne diseases:

* patronise licensed and reputable food premises, especially when eating high risk food like raw oysters;

* all foods, in particular shellfish, should be cooked thoroughly before consumption. Mud oysters should be cooked at boiling temperature for at least five minutes before eating;

* wash hands thoroughly with soap and water after using the toilet, before handling food or before eating;

* all food, especially shellfish, should be purchased from reliable and reputable suppliers;

* food handlers with symptoms of vomiting or diarrhoea should not handle food until they are symptom-free for at least two days; and,

* in the preparation of oysters, scald them in boiling water for not less than three minutes after washing them thoroughly.