Contaminated shellfish continue to cause disease in several European countries and Hong Kong.
In Helsinki, Finland, at least 170 people fell ill after eating oysters in various restaurants in February and March. Cases have also been reported in other Finnish cities.
Norovirus was found in nine different batches of oysters, two from the Netherlands, six from France, and one from Ireland. Importers have withdrawn the affected batches from the market.
Authorities tested food in restaurants, took patient samples, and found norovirus. Some of those sick reported eating oysters.
A report on the outbreak is being prepared for the Finnish Food Authority (Ruokavirasto) and the Finnish Institute of Health and Welfare (THL).
Norovirus is the most commonly identified cause of foodborne outbreaks in Finland. Between 2017 and 2021, oysters caused 11 norovirus outbreaks that sickened more than 110 people.
Finland has issued four Emergency Alert System for Food and Feed (RASFF) alerts for norovirus food poisoning in oysters since late February.
Overseas case
Sweden received three notifications in March. Norovirus in Swedish mussels infected seven people. Norovirus in oysters from France infected three of her, and norovirus in oysters from the Netherlands is suspected to be behind 15 diseases.
RASFF alerts have also been issued by Spain and Italy regarding norovirus in French oysters.
Harvesting areas have been closed and outbreaks have been reported in France, but it is unclear how many people have fallen ill.
In February, 20 people in Belgium were infected with norovirus in oysters from France. .
Two outbreaks in Denmark in late 2022 and early 2023 were caused by oysters. The first case, in which 19 people got sick, involved oysters from France, but of Irish origin. A second 73 cases were associated with Norwegian oysters.
Authorities in Hong Kong have reported several outbreaks related to raw oysters, including one from an Irish product that caused at least 16 illnesses earlier this year.
The Health Protection and Surveillance Center said there had been an increase in the number of norovirus cases and outbreaks reported in Ireland in the past few weeks, with the residential care sector particularly affected.
England has also seen a significant increase in norovirus cases, according to UK Health Security Agency (UKHSA) data.
Norovirus test reports are 77% higher than the five-season average for the same period before the coronavirus pandemic. The rise is seen across all age groups, but primarily in the He 65+ and Her Under 5 age groups.
The incubation period for norovirus illness is 12 to 48 hours. Symptoms include sudden cramps, abdominal pain, nausea, and then vomiting. Most people also have diarrhea. They usually last 12 to 72 hours.
Handwashing with soap and water is one of the keys to fighting viruses. Affected food industry staff should refrain from work for at least two days after symptoms stop to avoid spreading the infection. Norovirus can be transmitted directly from person to person through contaminated surfaces, food and drink.
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