Foodborne hepatitis A at a family reunion use of IgM-specific hepatitis a serologic testing

A cluster of cases of hepatitis A that occurred among 46 participants in a family reunion in Utah in August 1980 was investigated with epidemiologic and serologic techniques. No index patient with clinical illness had been present at the reunion. Twenty-three cases of hepatitis A were ultimately identified; 14 developed clinical hepatitis. Immunoglobulin M-specific hepatitis A virus antibody testing identified nine recently infected asymptomatic subjects. Eight additional individuals had serologic evidence of prior infection. Detection of these asymptomatically infected and nonsusceptible subjects among presumably well individuals led to the alteration of the food questionnaire analysis, ultimately implicating the green salad. The green-salad maker was identified as an asymptomatically infected individual and was thought to be the probable index case. Determination of hepatitis A virus antibody status of study subjects revealed age-related differences in clinical manifestations and disease susceptibility between individuals exposed to foodborne hepatitis A.