A New Zealand outbreak of norovirus gastroenteritis linked to the consumption of imported raw Korean oysters.

Aim: To investigate an outbreak of gastroenteritis that occurred following an international rugby test at Eden Park (Auckland, New Zealand) on 17 June 2006.

Method: 387 patrons were interviewed. Cases were defined as those from one of four hospitality areas who consumed food or beverage at Eden Park on the evening of 17 June 2006 and subsequently suffered from diarrhoea or vomiting; or, stomach cramps and nausea. A case-control study was conducted and food and beverage items associated with illness were identified. Clinical specimens were requested from patrons and food handlers, and leftover foods were analysed for pathogens. A food safety assessment was conducted at the implicated catering premises.

Results: A total of 115 cases were identified. Attack rates varied between the four hospitality areas from 8% to 47%. Predominant symptoms among cases included nausea, vomiting, diarrhoea, stomach cramps, fever, and chills. The consumption of several foods was associated with an increased risk of illness but the strongest was for raw oysters consumed in Hospitality Area 1 (Risk Ratio 11.9; 95%CI 3.9-36.1; p<0.00001), attack rate 65%. Norovirus (genogroups I and II) was detected in samples provided by four of the cases and three unopened packets of implicated batches of imported Korean Pacific oysters (Crassostrea gigas) linked to the outbreak.

Conclusion: This outbreak resulted from consumption of raw imported Korean oysters contaminated by norovirus. Labelling recommending cooking prior to consumption failed to prevent the outbreak.