STEAMING OYSTERS DOES NOT PREVENT NORWALK-LIKE GASTROENTERITIS

Objectives. To determine whether steaming oysters prevents gastroenter itis caused by small round structured (Norwalk-like) viruses and to id entify risk factors for illness. Methods. The authors interviewed ail 48 people who ate oysters at two church suppers that were followed by outbreaks of gastroenteritis from a Norwalk-like virus. Data were coll ected on demographics, clinical illness, number of oysters eaten, and the extent to which they were cooked. Results. Among the 48 persons, t he attack rate was 56%. The risk of illness increased with the number of oysters eaten (chi-square for trend = 5.7, P = 0.02). There was no decrease in attack rates among persons who ate oysters that were bette r done (chi-square for trend = 1.1, P = 0.29). Conclusions. In these o utbreaks, the risk of illness increased with the number of oysters eat en. Steaming oysters did not appear to prevent illness, suggesting tha t steaming may not be adequate to inactivate small round structured vi ruses. Public health messages that have emphasized the role of raw she llfish in the transmission of enteric viruses should be altered to inc rease the public's awareness that eating steamed oysters may also pose health risks.