Journal of Gastroenterology and Hepatology (2004) 19, 1305–1311 DOI: 10.1111/j.1400-1746.2004.03444.x Blackwell Science, LtdOxford, UKJGHJournal of Gastroenterology and Hepatology0815-93192004 Blackwell Publishing Asia Pty Ltd191113051311Original Article HCV infection in injecting drug usersY Satoh et al. Correspondence: Dr Keisuke Hino, Department of Laboratory Sciences, Faculty of Health Sciences, Yamaguchi University School of Medicine, Minamikogushi Ube, Yamaguchi 755-8505, Japan. Email: k.hino@yamaguchi-u.ac.jp Accepted for publication 1 December 2003. HEPATOLOGY Molecular epidemiologic analysis of hepatitis C virus infection in injecting drug users with acute hepatitis C in Japan YASUHIRO SATOH,* KEISUKE HINO, † TAKANOBU KATO, ‡ MASASHI MIZOKAMI, ‡ SATOYOSHI YAMASHITA, § HIROKI NAKAMURA* ,¶ AND KIWAMU OKITA* Departments of *Gastroenterology and Hepatology and † Laboratory Sciences, Yamaguchi University School of Medicine, Ube, ‡ Department of Clinical Molecular Informative Medicine, Nagoya City University Graduate School of Medical Sciences, Nagoya, § Department of Gastroenterology, Shimonoseki Kohsei Hospital, Shimonoseki, and ¶ Department of Gastroenterology, Hagi Civil Hospital, Hagi, Japan Abstract 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 his- tory 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 genet- ically 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 transmit- ted between IDUs very recently in Yamaguchi prefecture, Japan. © 2004 Blackwell Publishing Asia Pty Ltd Key words: chronic hepatitis C, hepatitis C virus E2 gene, phylogenetic analysis. INTRODUCTION Approximately 15 years have passed since the discov- ery of hepatitis C virus (HCV) in 1989 and assays became available for the detection of antibodies. Dur- ing this period HCV infection through transfusion of blood products has become a rare event in industrial- ized countries, following the introduction of current screening strategies in the early 1990s. 1,2 Instead, intra- venous (i.v.) drug use is presently the most important risk factor for HCV infection. The increased risk is associated with the sharing of contaminated equipment between injecting drug users (IDUs). 3–6 The prevalence of HCV infection among IDUs is estimated to be between 30 and 90%. 7–9 Particular HCV subtypes have been shown to be associated with injecting drug use in Western Europe. 10–14 This phenomenon has also been observed in central and Eastern Europe, where the size of the illicit drug market increased after political changes took place in 1989. 15–17 These results suggest that infection with a particular HCV genotype or sub- type is spreading and is potentially being accumulated