Genotype distribution and molecular epidemiology of hepatitis C virus in blood donors from southeast France

Abstract

The genotype distribution of hepatitis C virus (HCV) in blood donors from southeast France was tracked for a period of 13 years (1991 to 2003). Virus genomes from 321 samples were analyzed by amplification and sequencing of the NS5b and E1 regions. The most frequent genotypes were 1b (30.2%), 1a (27.7%), and 3a (22.4%). Although it was less common, genotype 2 was characterized by the presence of strains belonging to 11 different subtypes, including 5 that had never been characterized. Genotypes 1a, 1b, 3a, and 4a presented typical "epidemic" profiles, with a large number of isolates per subtype and short mean genetic distances between isolates. Type 2 isolates displayed a typical "endemic" profile, with a large number of subtypes and very few isolates in each subtype. The epidemiology of HCV infection in southeast France changed radically during the study period in relation to modifications in the etiology of infection. We observed the emergence of new epidemic subtypes (subtypes 1a and 3) linked to intravenous drug use and a decrease in the types linked to blood transfusion and nosocomial infection (epidemic subtype 1b and endemic type 2). Comparison of strains from blood donors with strains from a cohort of inpatients in the same region during 2001 and 2002 demonstrated for the first time that the monitoring of blood donors is a generally valid indicator of HCV epidemiology in terms of genotype distribution.

FIG. 1.

Phylogenetic tree of partial NS5b nucleotide sequences of 33 HCV strains isolated from blood donors (++) and a panel of reference strains identified by their GenBank accession numbers. New subtypes are indicated by arrowheads. The numbers at the right correspond to prototype strain subtypes as previously published by Stuyver et al. (33) for subtypes 2a, 2b, 2c, 2d, 2e, 2f, 2k, and 2l and Tokita et al. (39) for subtypes 2e* and 2f*. The numbers at the nodes are the percentages of 1,000 bootstrap replicates higher than 50%. The scale bar indicates the p distances. The vertical dotted line represents separation between subtypes.

FIG. 2.

Distribution of hepatitis C virus types according to date of collection. The number of cases is indicated in parentheses.