European baseline survey of norovirus in oysters

The European Commission requested scientific technical assistance for a European Union coordinated monitoring programme on the prevalence of norovirus (NoV) in raw oysters. The objective of the survey is to estimate the... [ view full abstract ]

The European Commission requested scientific technical assistance for a European Union coordinated monitoring programme on the prevalence of norovirus (NoV) in raw oysters. The objective of the survey is to estimate the European prevalence of norovirus-contaminated oysters at production areas and batches of oysters at dispatch centres, with a 95% level of confidence and a level of precision of 5% considering an expected prevalence of 50%. The sample unit in production areas is a classified production area actively growing commercial oysters (whether harvesting or not is occurring) and for dispatch centres is a quantity of live oysters which are being packed and labelled with an Identification Mark. Based on a multistage sampling scheme, 1,026 samples from 171 production areas and 1,182 samples from 197 dispatch centres in 13 EU member States or EFSA countries should be taken annually. The samples are to be analysed according to the method specification developed by the expert working group led by the European Union Reference Laboratory (EURL), which is compliant with ISO 15216-1. Data reporting is via the EFSA data collection framework. The survey started on 1 Nov 2016 and finishes on 31 Oct 2018. Issues identified so far, are the transient nature of dispatch centres and difficulties in collecting information for batches of mixed origin. Generalised linear models will be used to estimate proportion (with 95% confidence intervals) of sample units with NoV contamination for the following thresholds: < limit of quantification (LOQ), 100, 200, 500, 1,000, 5,000, 10,000 and > 10,000 copies/g.