Changing prevalence of hepatitis B virus in urbanized Australian aborigines.

Serological surveys of desert or rural Australian Aboriginal settlements report up to 85% positivity for hepatitis B virus (HBV) markers. We report the results of two cross-sectional HBV surveys carried out 5 years apart in the bi-racial town of Condobolin, New South Wales (population 3086; 14% Aborigines). In 1983-84, none of the 310 non-Aborigines tested were hepatitis B surface antigen (HBsAg) positive but 7.2% were positive for hepatitis B core antibody (anti-HBc). Among Aboriginal subjects, 57.6% had detectable HBV markers and 16.9% were HBsAg positive. In 1987-88, no non-Aborigines were HBsAg positive and only 1% (of 422 individuals) had anti-core antibodies. In contrast, 36% of Aboriginal subjects had HBV markers and 6% were HBsAg positive. No significant difference in detectable HBV markers was found among 98 Aborigines who were included in both surveys. Migration was the main factor influencing the HBV prevalence between the two surveys. Clustering of HBsAg carriers occurred within households and the likely mode of infection was intrafamilial horizontal childhood transmission. There was a significant association between HBV markers and tattooing in Aborigines (P < 0.02). Overall, HBV markers were less frequent in this population than in other desert or rural Aboriginal populations surveyed. The prevalence of HBV infection in non-Aboriginal households was not significantly different from that in the Australian Caucasian population.