Local spread of HDV infection transiently occurring in Japan

Hepatitis B virus (HBV) carriers and patients with acute hepatitis B living in the Kamigoto islands, a part of Japan with a high incidence of HBV carriage, were retrospectively tested for serum anti-hepatitis D virus (anti-HDV) and they were compared with the inhabitants of Oita City (an area with an average HBV carriage rate). The prevalence of anti-HDV in HBV-infected individuals was 8.3% (42/507) in Kamigoto and 0% (0/101) in Oita City. With one exception, all of the positive serum samples in Kamigoto were collected before 1986, and the mean age of the positive individuals was significantly younger than that of the negative individuals (P < 0.005). Among the 42 anti-HDV-positive patients, nine (21%) had definite liver disease. The route of infection was uncertain in most cases (i.e. sporadic), but two pairs of mothers and children were detected. Although the prevalence of anti-HDV positivity in Japan has been reported to be very low (about 1% or less), the present investigation showed that the local spread of HDV infection in Kamigoto occurred on a minor scale up to 1986. The infections presumably resulted from the closed environment and the high incidence of HBV carriage in these islands. Accordingly, there could be a considerable risk of the outbreak of HDV infection in the future under similar conditions, even in countries where the disease has never been detected previously.