Objectives: Acute viral hepatitis A infection in adults is an emerging public health problem in Korea. The infectivity and pathogenicity of hepatitis A virus (HAV) in close contact have not been studied previously. This study investigated the secondary attack rate and pathogenicity rate of HAV during an outbreak among auxiliary police in a communal living.
Methods: A total of 70 people in close contact with a hepatitis A patient (index case) were enrolled in the study, which included a thorough oral history, physical examination, and laboratory testing. The subjects were part of an auxiliary police unit living in a communal setting (HAV contact group). Specific antibodies in the sera were determined at the time when the last hepatitis patient was discharged from hospital and at the end of the longest incubation periods. Subjects in another auxiliary police unit without exposure to hepatitis A were examined as a control group (HAV non-contact group). The secondary attack rate and pathogenicity rate were calculated from the data.
Results: In the HAV non-contact group, none of the subjects had anti-HAV antibodies. In the HAV contact group, three subjects had both IgM and IgG anti-HAV antibodies, and two had only IgG anti-HAV antibodies. Two of three (or five) HAV-infected subjects were treated for hepatitis A..
Conclusion: The secondary attack rate (infectivity) of HAV was 4.3 - 7.1% (3~5/70) and the pathogenicity rate was 40.0 ~ 66.7% in the group of young adults.