The number of food poisoning cases involving raw oysters has surged dramatically this winter compared to last year.

According to the Ministry of Food and Drug Safety on Tuesday, a total of 524 cases of food poisoning due to raw oysters were reported between November 2022 and February 2023. This figure is an eightfold increase compared to the same period between 2021 and 2022, which only had 68 cases.

Oysters are rich in minerals and vitamins but can be one of the main sources of the norovirus, which is more common in winter.

The norovirus causes vomiting, diarrhea, stomach pain and muscle aches after a 12-to-48-hour incubation period. The illness runs its course in fewer than three days but can spread very easily through close contact or via contaminated food or surfaces.

For prevention of food poisoning caused by the norovirus, health officials recommend that foods be heated or cooked at 85 degrees for more than 1 minute.

Consuming oysters harvested in unauthorized areas also poses dangers of exposure to shellfish toxins. These toxins can cause severe and life-threatening neurological effects. Symptoms include muscle weakness, disorientation and short-term memory loss.