An agency in Ireland has published a notice to try to reduce the incidence of contaminated oysters in the market and minimize norovirus-related illnesses.

The Sea-Fisheries Protection Authority (SFPA) Food Safety Information Notice covers strategies to manage norovirus risks in oysters.

It coincides with the SFPA and Food Safety Authority of Ireland’s (FSAI) annual food safety workshop in late February, which focused on norovirus and food incidents.

Norovirus is transmitted through the consumption of food or water contaminated with fecal matter or through contact with infected individuals or surfaces. The virus can be present in discharges from wastewater treatment systems.

Recent illnesses reported

Bivalve mollusks such as oysters are known to accumulate and concentrate norovirus. This poses a health risk as these shellfish are often consumed raw or lightly cooked, making them a potential source of infection. There is no regulatory limit for norovirus relating to shellfish.

In March, two people in Spain and three in Finland fell sick with norovirus after eating oysters from France. Oysters from Ireland were linked to two norovirus cases in Finland. Norovirus in a seaweed salad from China sickened three people in Italy. Norovirus in oysters from the Netherlands affected two people in Belgium.

In separate incidents in February, three people were ill in France after eating oysters, and five cases were reported in Spain. Also in February, the Netherlands issued a Rapid alert System for Food and Feed (RASFF) alert for rotavirus in oysters from Ireland. In March, France reported E. coli in Irish mussels.

SFPA said businesses involved in oyster production must be aware of the risk and implement appropriate management actions, especially during the high-risk winter period. These measures should be part of their food safety management system, adhering to Hazard Analysis and Critical Control Points (HACCP) principles.

Related advice and workshop

Guidance to help mitigate the risk of norovirus contamination in oysters has been developed by the SFPA, FSAI, the Marine Institute, and Bord Iascaigh Mhara (BIM).

Risk factors for shellfish-related norovirus include cold weather, low water temperatures, and high rainfall, potentially leading to sewage system overflows.

The only laboratory in Ireland currently doing norovirus testing in shellfish is the Marine Institute. Still, due to resource and scheduling issues, only a restricted number of samples can be tested. It is expected that, given demand, private commercial labs will begin to provide norovirus testing in the future. Private labs in the UK and elsewher can provide such testing.

SFPA, FSAI, and the Marine Institute also hosted a workshop for industry in February on the requirements relating to sanitary surveys for shellfish harvesting areas and Ireland’s implementation of the related legislation.

SFPA presented data management and shellfish classification and gave an updat on the sanitary survey program in Ireland. The keynote speaker was Michelle Price-Howard from the Centre for Environment, Fisheries, Aquaculture and Science (CEFAS).