Trends in the total numbers of HBV and HCV carriers in Japan from 2000 to 2011.

We estimated the total number of undiagnosed HBV and HCV carriers and patients with hepatitis virus-related disease in Japan according to 6 different groups classified by their natural histories during 2011. In 2011, the total number of carriers and patients infected with HBV or HCV was estimated according to 6 groups using government reports and reports from the hepatitis epidemiology research group of The Ministry of Health, Labor and Welfare in Japan. In 2011, the total number of hepatitis virus carriers was estimated to be 2090128-2840128 in which the estimated number of undiagnosed HCV and HBV carriers was 776826 (HBV: 481470; HCV: 295356). The total number of treated patients, as either inpatients or outpatients, was estimated to be 811588 (HBV: 303366; HCV: 520600) in 2011. It is presumed that many carriers shirk consultation for many reasons, such as patients' misunderstanding, lack of awareness and forgetfulness of their positive status. The numbers of infected patients who did not seek treatment increased gradually to 501714-1251714 (HBV: 333791-483791; HCV: 167923-767923) in 2011. Compared to 2000, the number of undiagnosed carriers was significantly reduced in 2011 probably because of the well-organized, effective national hepatitis virus screening system that has been launched by the Japanese government since 2002. Moreover, the increase in the number of untreated persons who are aware of their positive status shows that more effort should be invested in improving the referral system from screening centres to core hospitals.