Total Numbers of Undiagnosed Carriers of Hepatitis C and B Viruses in Japan Estimated by Age- and Area-Specific Prevalence on the National Scale

Objective: To estimate total numbers of undiagnosed carriers of hepatitis C virus (HCV) and hepatitis B virus (HBV) in Japan. Methods: Area- and age-specific prevalence of HCV as well as HBV was determined in the first-time blood donors [20-39 years (n = 2,429,364)] and examinees of periodical health check-ups [40-74 years (6,204,968 for HCV and 6,228,967 for HBV)] in Japan. Prevalence in adolescents [5-19 years (79,256 for HCV and 68,792 for HBV)] was determined in a single prefecture, and that of HCV in the elderly (6 75 years) was estimated by the exponential model. HBV infection was determined by the detection of hepatitis B surface antigen, and HCV infection by either the algorithm or assuming persistent infection in 70% of the individuals with antibody to HCV. Results: Of the total population of 127,285,653 in 2005, 807,903 (95% CI 679,886-974,292) were estimated to be infected with HCV at a carrier rate of 0.63%, and 903,145 (837,189-969,572) with HBV at that of 0.71%. Conclusion: Accurate estimation of undiagnosed HCV and HBV carriers in the general population would help to predict the future burden of liver disease, and take appropriate measures for improving healthcare. Copyright (C) 2011 S. Karger AG, Basel