An outbreak of hepatitis A associated with green onions

Forty-three cases of serologically confirmed hepatitis A occurred among ind ividuals who ate at restaurant A in Ohio in 1998. Serum samples from all re staurant A employees who worked during the exposure period were negative fo r IgM antibodies to hepatitis A virus (HAV). A matched case-control study d etermined that foods containing green onions, which were eaten by 38 (95%) of 40 case patients compared with 30 (50%) of 60 control subjects, were ass ociated with illness (matched odds ratio, 12.7; 95% confidence interval, 2. 6-60.8). Genetic sequences of viral isolates from 14 case patients were ide ntical to each other and to those of viral isolates from 3 patients with ca ses of hepatitis A acquired in Mexico. Although the implicated green onions , which could have come from one of 2 Mexican farms or from a Californian f arm, were widely distributed, no additional green onion-associated cases we re detected. More sensitive methods are needed to detect foodborne hepatiti s A. A better understanding of how HAV might contaminate raw produce would aid in developing prevention strategies.