[Epidemiological study of hepatitis B and C virus in Okinawa and Kyushu, Japan]

Epidemiological studies of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection in Okinawa and Kyushu have been conducted since 1970. Early in the study period, the prevalence of HBsAg on Iriomote and Hateruma islands in Okinawa was 9.0% and 6.1%, respectively, which were significantly higher than the 2.4% in Kyushu. Prevalence of anti-HBc on Iriomote island was 59.8% and that on Hateruma island 70.9%, also which were significantly higher than the 30.9% in Kyushu. Prevalence of HBV infection has been observed in both Okinawa and Kyushu with prevalences of HBsAg in Okinawa decreasing from 11.6% in 1970 to 3.8% in 1988 and in Kyushu from 2.1% in 1980 to 0.7% in 1991. Prevalence of anti-HCV in Okinawa was only 0.7%, while the prevalence was 3.4% in Kyushu when measured by C100-3 and anti-GOR. In Kyushu, the prevalence of anti-HCV advanced with age and reached a peak in the population 60 years of age. HCV transmission occurs mainly by blood transfusion. We investigated the systems of blood supply in Okinawa and Kyushu. In Japan, including Kyushu, paid blood was mainly used from 1955 to 1969, but in Okinawa it was donated by relatives and friends. The difference in blood supply between these areas may be a cause of the differing of HCV infection.