Changing patterns in the distribution of hepatitis B subtypes.

From July 1, 1969, to June 30, 1977, 4,413 patients with acute viral hepatitis were admitted to Fairfield Hospital, Melbourne, of whom 1,128 (25.6%) had hepatitis type B. Only two of the four major subtypes of hepatitis B surface antigen (HBsAg) were detected, HBsAg/ayw and HBsAg/adw, and of these HBsAg/ayw was present in 80.4% of cases. Over the 8-year period, hepatitis B became more common in Melbourne and the proportion of patients infected with the ayw subtype increased from 75 to 91%. Approximately 50% of the patients with hepatitis B were intravenous drug abusers. In most of the others the source of infection was unknown.