Seroepidemiological study of hepatitis delta virus infection in Okinawa, Japan

A seroepidemiological study on hepatitis delta virus (HDV) infection was conducted in the Okinawan islands, the area of Japan where hepatitis B virus infection is most prevalent. The subjects of this study included 116 asymptomatic hepatitis B surface antigen (HBsAg) carriers, 48 patients with chronic hepatitis (CH), 19 with liver cirrhosis (LC), and 11 with hepatocellular carcinoma (HCC). Among the 194 serum samples examined, a total of 10 (5.2%) were anti-HDV seropositive. Anti-HDV was detected in 2 (1.7%) of the 116 asymptomatic HBsAg carriers, in 3 (6.3%) of the 48 patients with CH, and in 5 (26.3%) of the 19 with LC. However, none of the patients with HCC had detectable anti-HDV. Eight of the 10 were born in the Miyako island group and the remaining 2 on the main island of Okinawa. Since the subjects included 34 individuals who were living and/or born in the Miyako islands, the positive rate of anti-HDV in the islands was 23.5%. This study demonstrates the existence of an endemic area of HDV infection in Japan.