In addition to the diagnosed cases of illness in Sweden, the National Food Agency suspects a large dark figure, since it is not obvious to link the disease with oysters. The symptoms have in most cases coincided with the noron virus, also called winter malaise. The virus has been found in oysters both in Sweden and in other countries.
In some cases, Swedish-grown oysters have also caused nausea.
It is not uncommon for oysters to cause stomach upset in winter, but in December and January the cases have been unusually numerous, according to the National Food Agency.
The oyster scandal hits hard in some regions of France. On Thursday morning, SVT's European correspondent Christoffer Wendick told how the situation arose and how it affects the oyster industry.