Seroepidemiological study on hepatitis delta virus infection in the Irabu Islands, Okinawa, Japan

A seroepidemiological study was performed to clarify the prevalence of hepatitis delta virus (HDV) infection among the general population in the Irabu islands, Okinawa, Japan. Of 2028 healthy people examined who had received their annual health check-up in 1994-95, 195 (9.6%) were positive for hepatitis B surface antigen (HBsAg). Of these 195 HBsAg-positive individuals, 46 (23.6%) showed a positive reaction for antibody to HDV (anti-HDV). The positivity rate of anti-HDV among HBsAg-positive subjects tended to increase with age up to 50-59 years of age. The prevalence of anti-HDV also varied among the seven districts in the islands (0-63.3%). None of the anti-HDV-positive subjects was included in the high risk group for parenterally transmitted diseases. The unusually high prevalence of anti-HDV among HBsAg-positive individuals, particularly in the older age groups, seemed to reflect the natural prevalence or previous HDV infection, rather than a current or imported infection of HDV. Although the great majority of HBsAg-positive subjects with anti-HDV were asymptomatic, abnormally high values of serum transaminases were more frequently seen in these subjects compared with HBsAg-positive subjects without anti-HDV.