Evidence of a large, international network of HCV transmission in HIV-positive men who have sex with men.

BACKGROUND & AIMS Since 2000, there has been a marked rise in acute hepatitis C virus (HCV) in human immunodeficiency virus (HIV)-positive men who have sex with men (MSM). We conducted an international phylogenetic study to investigate the existence of an HCV transmission network among MSM. METHODS HIV-positive MSM diagnosed with recent HCV (n = 226) in England (107), The Netherlands (58), France (12), Germany (25), and Australia (24) between 2000 and 2006 were enrolled into a molecular phylogenetic study. Using real-time polymerase chain reaction (PCR), the NS5B region of the HCV genome (436 base pair) was amplified, sequenced, and compared with unrelated NS5B sequences. RESULTS NS5B sequences were obtained from 200 (89%) cases. Circulating HCV genotypes were 1a (59%), 4d (23%), 3a (11%), 1b (5%), and 2b/c (3%). Phylogenetic analysis revealed 156 (78%) sequences that formed 11 clusters (bootstrap value > 70%) containing between 4 and 37 individual sequences. Country mixing was associated with larger cluster size (17 vs 4.5 sequences; P = .03). "Molecular clock" analysis indicated that the majority (85%) of transmissions occurred since 1996. CONCLUSIONS Phylogenetic analysis revealed a large international network of HCV transmission among HIV-positive MSM. The rapid spread of HCV among neighboring countries is supported by the large proportion (74%) of European MSM infected with an HCV strain co-circulating in multiple European countries, the low evolutionary distances among HCV isolates from different countries, and the trend toward increased country mixing with increasing cluster size. Temporally, this epidemic coincides with the introduction of highly active antiretroviral therapy and associated increases in sexual risk behaviors. International collaborative public health efforts are needed to mitigate HCV transmission among this population.