Present state of hepatitis E virus epidemiology in Tokyo, Japan

Recently studies have reported the possibility that an indigenous hepatitis E virus (HEV) exists in Japan, but the epidemiological features of HEV in Japan are inadequate to make a judgment. In order to search the present state of HEV infection in Japan, we used ELISA to test 1033 sera from residents living in Tokyo and the Tokyo suburbs, for the presence of the antibody against HEV. The positive rate of anti-HEV IgG was 15.4% in all liver disease patients (68 of 440), 3% (6/200) in healthy individuals and 0.4% in infants (1/246), respectively (P<0.01). Anti-HEV IgG was seen in 17.6% (35/199) of liver disease patients of unknown etiology; 29.4% (5/17) of fulminant hepatitis, 17% of acute hepatitis (15/88) and 16% of chronic hepatitis (15/94). Anti-HEV IgG co-existed with hepatitis B virus and hepatitis C virus in 23.6% (21/89) and 7.9% (12/152), respectively. Furthermore, the prevalence of anti-HEV IgG was significantly higher in hemodialysis patients (18/60: 30%) and hospital workers (8/87: 9.2%) than in the healthy population (P<0.01). Anti-HEV IgM was detected in 0.1% of all samples tested (1/1033). The prevalence of anti-HEV IgG increased with age. No individuals with HEV antibody had a recent history of visiting countries where hepatitis E is endemic. These results indicate that generally 15.4% of Japanese patients with liver diseases had a history of HEV infection in the past. The routes of transmission of HEV require clarification in Japan.