Commentary. An outbreak of Norwalk virus gastroenteritis following consumption of oysters.

While the only laboratory evidence for Norwalk virus infection was a positive PCR result from a single stool, the symptom profile, incubation period, and duration of illness are entirely consistent with previous outbreaks of Norwalk virus infection. In similar outbreaks where the symptoms, incubation period, and duration of illness suggest a viral aetiology, RT-PCR, as used in this investigation could be increasingly utilized. This technique is estimated to detect as little as 10 to 1,000 Norwalk virus particles per millilitre of stool compared to a lower level of detection of 10 to10 particles per millilitre of stool by electron microscopy.