Multistate Outbreak of Hepatitis A Associated with Frozen Strawberries

A multistate outbreak of hepatitis A was traced to frozen strawberries processed at a single plant. Among 827 students and 60 teachers at an elementary school in Georgia during a 2-week period, 15 developed hepatitis A. Three months later, among 174 residents and 467 staff in an institution for the developmentally disabled in Montana during a 3-week period, 13 developed hepatitis A. Primary attack rates were 10% in the school and 8% in the institution. Cohort analysis in the school implicated consumption of strawberry shortcake in hepatitis A virus (HAV) infection (relative risk, 7.6; 95% confidence interval, 1.04-55.6). In the institution, such analysis implicated desserts and uncooked strawberries as the most biologically plausible vehicle of HAV transmission. Molecular analysis of HAV from patients in the two outbreaks revealed that the viral genomes were genetically identical and distinct from other known US strains. Contamination of food products before retail distribution is rare but should be considered in investigating common-source outbreaks of hepatitis A.