Abstract: Objective To asses the correlation factors of a hepatitis A outbreak.Methods A 1:2 case-control study was carried out,56 cases of acute hepatitis A and 112 controls were interviewed.A questionnaire was administered to all subjects by one of the authors.Odds ratios and their 95% confidence limits were computed.Results Jiaban shrimp was the dietary factor of hepatitis A outbreak.The relative risk of eating raw Jiaban shrimps were 19.82 times than that of no eating,and there existence relationship of dosage-reaction.Conclusion Jiaban shrimps were the correlation factor of hepatitis A out-break.The department concerned should enhance the sanitary administrating and hepatitis A virus monitoring to seamost products.