Molecular epidemiologic analysis of hepatitis C virus infection in injecting drug users with acute hepatitis C in Japan

BACKGROUND AND AIM: The aim of this study was to examine whether particular hepatitis C virus (HCV) subtypes are spreading among injecting drug users (IDUs) in Yamaguchi prefecture, on the south-western tip of the island of Honshu in Japan, as found in European countries. METHODS: We prospectively enrolled acute hepatitis C patients from January 2001 to March 2003. E2 gene sequences of HCV isolates from IDUs with acute hepatitis C were phylogenetically compared to those from 30 chronic hepatitis C patients with the same HCV subtypes who had or did not have a history of intravenous drug use. RESULTS: Nine of 11 patients (82%) with acute hepatitis C were IDUs. The HCV subtypes were 2a in four and 2b in five, which contrasted with the high prevalence of subtype 1b in patients with chronic liver diseases in Japan. IDUs with acute hepatitis C (22.0 +/- 2.4 years old) were significantly younger than those with chronic hepatitis C (49.5 +/- 9.5 years old) for subtype 2a (P = 0.0005), but not for subtype 2b (25.6 +/- 5.4 vs 28.1 +/- 2.4 years old). Some HCV isolates of subtype 2b from IDUs with acute hepatitis C were phylogenetically related to those from IDUs with chronic hepatitis C. By contrast, there was no phylogenetic segregation of HCV in IDUs with subtype 2a. HCV isolates from non-IDUs were genetically divergent from each other and those from IDUs, irrespective of the HCV subtype. CONCLUSION: Hepatitis C virus of the non-1b subtype, particularly subtype 2b, seemed to be transmitted between IDUs very recently in Yamaguchi prefecture, Japan.