Phylogenetic analyses confirm the high prevalence of hepatitis C virus (HCV) type 4 in the Seine-Saint-Denis district (France) and indicate seven different HCV-4 subtypes linked to two different epidemiological patterns

Laboratoire de Bactériologie, Virologie-Hygiène, Hôpital Avicenne, Equipe d’accueil Agents Transmissibles et Hôtes, Signalisation Cellulaire et Oncogenese, UFR Santé Médecine Biologie Humaine, Université Paris 13, Bobigny, France 1 Services d’Hépatologie-Gastroentérologie, Réseau hépatite C Nord-Est Parisien, Hôpitaux Avicenne et Jean Verdier, UFR Santé Médecine Biologie Humaine, Université Paris 13, Bobigny et Bondy, France 2 Services de Médecine Interne et de Maladies Infectieuses et Tropicales, Centre d’Information et de Soins de l’Immunodéficience Humaine du 93 (CISIH 93), Hôpitaux Avicenne et Jean Verdier, UFR Santé Médecine Biologie Humaine, Université Paris 13, Bobigny et Bondy, France 3 Service de Microbiologie, Unité de Virologie, CHU de Bicêtre, Le Kremlin-Bicêtre, France 4 Author for correspondence: Paul Dény. Fax +33 1 48 95 59 11. e-mail paul.deny{at}avc.ap-hop-paris.fr Hepatitis C virus (HCV) has been classified into six clades as a result of high genetic variability. In the Seine-Saint-Denis district of north-east Paris, the prevalence of HCV-4, which usually infects populations from Africa or the Middle East, is twice as high as that recorded for the whole of continental France (10·2 versus 4·5%). Although the pathogenicity of HCV-4 remains unknown, resistance of HCV-4 to therapy appears to be similar to that observed for HCV-1. In order to characterize the epidemiology of HCV-4 in Paris, sequences of the non-structural 5B gene (332 bp) were obtained from 38 HCV-4-infected patients. Extensive phylogenetic analyses indicated seven different HCV-4 subtypes. Moreover, phylogenetic tree topologies clearly distinguished two epidemiological profiles. The first profile (52·6% of patients) reflects the intra-suburban emergence of two distinct HCV-4 subclades occurring mainly among intravenous drug users (65% of patients). The second profile shows six subclades [HCV-4a, -4f, -4h, -4k, -4a(B) and a new sequence] and accounts for patients from Africa (Egypt and sub-Saharan countries) who have unknown risk factors (77·8% of patients) and in whom no recent diffusion of HCV-4 is evident. This study indicates the high diversity of HCV-4 and the extension of HCV-4a and -4d subclades among drug users in France.