Following a flooding event close to a shellfish production lagoon, 205 cases of gastroenteritis were linked to oyster consumption. Twelve stool samples from different individuals were collected. Analysis showed that eight samples were positive for multiple enteric viruses, and one stool sample had seven different enteric viruses. Analysis of shellfish implicated in the outbreak allowed detection of the same diversity of enteric viruses, with some viral genomic sequences being identical to those obtained from stool sample analysis. Shellfish were contaminated by as many as five different enteric viruses. For the first time in Europe, Aichi virus was identified in oyster samples. Shellfish samples collected over 3 weeks following the outbreak showed a progressive decline in the level of virus contamination as measured by the virus diversity detected and by quantitative reverse transcription-PCR.(R.A.)