Viral hepatitis: a four-year hospital and general-practice study in Sydney. 2. Transmission of viral hepatitis among residential contacts in Sydney.

Clinical and serological study of household contacts of index patients suffering from acute viral hepatitis showed the high infectivity of hepatitis A viral (HAV) for susceptible contacts. The anti-HAV specific IgM developed in sera of 67% of susceptible children and 31% of susceptible adult contacts. Of 81 susceptible contacts whose sera became anti-HAV positive, 28.4% developed clinically overt hepatitis. Administration of human immunoglobulin reduced the rate of clinical expression of hepatitis A among susceptible contacts; it also appeared to reduce the actual infection rate. The infection rate among susceptible adult contacts of adult index cases suffering from hepatitis B was 24%. Of 25 susceptible contacts whose sera became HBV-marker positive, 24% developed clinical illness. Transmission occurred probably both by parenteral and non-parenteral means. It is currently not possible to determine susceptibility or seroconversion to hepatitis non-A non-B agents.