A preliminary serologic study of hepatitis A virus infection in Japan.

Ninety-eight acute non-B hepatitis cases recently observed in Japan and household contacts with these cases were subjected to serologic examinations for hepatitis A; 400 serum specimens obtained in 1971 from healthy individuals living in areas near Tokyo and 16 preparations of human immunoglobulin produced in Japan in 1975 and 1976 were examined for antibody to hepatitis A antigen. Hepatitis A virus infection was confirmed in all 25 patients and in 8 of 26 household contacts found in association with non-B hepatitis outbreaks, and also in 11 of 60 sporadic non-B hepatitis patients, but in none of 13 non-B hepatitis patients found in association with blood transfusion. There was no difference between males and females in the prevalence of antibody to hepatitis A antigen among healthy individuals, however, there was a strong relationship to age. Rates of antibody positives were only 2.5% in the groups younger than 20 years of age. An ample amount of antibody to hepatitis A antigen was detected in the preparations of human immunoglobulin. Hepatitis A virus was thus found to be endemic in Japan, but considered not popular during at least these 20 years. Infection with non-A non-B hepatitis virus(es) seems to be common in Japan especially in such cases as sporadic non-B hepatitis or post-transfusion non-B hepatitis.