Abstract
The mortality due to hepatocellular carcinoma (HCC) has ranged widely in various areas of Japan since 30 years ago and the incidence was particularly high in once
Schistosoma japonicum (
Sj)-endemic areas. Our aim was to estimate the spread time of hepatitis C virus (HCV) infection in the past with possible relevance to a higher incidence of HCC in once
Sj-endemic than
Sj-nonendemic areas.
During 2001, 131 strains of HCV-1b were obtained from patients in three previously
Sj-endemic areas, as well as
Sj-nonendemic areas in Japan and a cross-sectional study was conducted on them with molecular evolutionary analyses.
A phylogenetic tree reconstructed on HCV-1b sequences in the NS5B region disclosed 2 independent clusters for
Sj-positive and -negative groups with a high bootstrap value. The estimated effective number of HCV-infections indicated a transition from quiescence to rapid exponential growth in the 1920s among patients with schistosomiasis, which is 20 years earlier than that among patients without schistosomiasis.
The estimated spread time in previously
Sj-endemic areas in Japan coincides with injection treatment for
Sj since 1921. A high incidence of HCC there would be attributed to a long duration of HCV infection since 1920s.