Current methods used to remove norovirus in shellfish are not an effective means of reducing contamination. The Panel recommends establishing acceptable limits for the presence of virus in oysters that are harvested and placed on the market in the European Union. In addition, an EU-wide baseline survey on norovirus in oysters should be carried out to provide information on overall consumer exposure as well as the public health impact of control measures.
Norovirus, sometimes referred to in the media as the “winter vomiting bug”, is a major cause of acute gastroenteritis in Europe often causing diarrhoea and vomiting. The virus is transmitted through the consumption of food or water contaminated with faecal matter or more often through person-to-person contact or contact with infected surfaces. Bivalve molluscs such as oysters and scallops are a well documented source of infection as they can accumulate and concentrate virus particles. Oysters contaminated with norovirus pose a particular risk to human health as they are often consumed raw.
EFSA’s BIOHAZ Panel concludes that norovirus is highly infectious and that the amount of the virus detected in oysters linked to human cases can vary greatly. Scientists highlight that norovirus is frequently detected in oysters in Europe which comply with existing EU control standards for bivalve molluscs.
EFSA evaluated the detection methods and control options for norovirus in oysters. The assessment looked at the use of a technique (the PCR method already applied to other shellfish for the detection and quantification of norovirus in oysters, the possibility of defining a level at which the presence of the virus in oysters would be unlikely to pose a risk to consumers and possible post-harvest control options. The Panel considers that the PCR method is suitable for detection and quantification of norovirus in oysters provided that appropriate quality assurance measures are implemented.
More information and the opinion may be found on the EFSA Web site.