Contaminated oysters are continuing to cause illnesses in several European countries and Hong Kong.
At least 170 people have fallen ill in Helsinki, after eating oysters in different restaurants in February and March. Cases have also been reported in other Finnish cities.
Norovirus has been found in nine different oyster batches. Importers have withdrawn affected batches from the market.
A report on the outbreak is being prepared for the Finnish Food Authority and the Finnish Institute for Health and Welfare. Norovirus is the most commonly identified cause of foodborne outbreaks in Finland. Between 2017 and 2021, oysters caused 11 norovirus outbreaks in which more than 110 people fell ill.
Cases in other countries
There has been two outbreaks in Denmark from late 2022 to early 2023 caused by oysters. The first where 19 people got sick from eating oysters from France. The second with 73 cases that was linked to oysters from Norway. Sweden have had three notifications in March where seven people fell ill.
Authorities in Hong Kong have reported several outbreaks linked to raw oysters including one that caused at least 16 people to get sick earlier this year.
The Health Protection Surveillance Centre said there had been an increase in the number of norovirus cases and outbreaks.
The incubation period for illness caused by norovirus is 12 to 48 hours. Symptoms includes cramping, abdominal pain, and nausea, followed by vomiting. They usually last 12 to 72 hours.
Norovirus can be transmitted directly from one person to another and through contaminated surfaces, food, and beverages.