Phylogenetic tree-based epidemiological analysis of hepatitis C virus transmission in a region of Japan with a high prevalence of infection

Abstract

Local clustering of hepatitis C virus (HCV) infection has been demonstrated in various regions in Japan. HCV genotypes have now been compared between infected individuals from districts of Saga prefecture with either a high (H district) or low (L district) prevalence of HCV-seropositivity. The prevalence of HCV genotype 1b was significantly higher (P < 0.001) in the H district (45/50; 90%) than in the L district (19/36; 52.8%). A phylogenetic tree was constructed based on the genomic sequences of viral isolates from 20 patients infected with genotype 1b in the H district. Almost all these HCV strains clustered in the same regions of the tree. With regard to risk factors for HCV transmission, the percentage of patients with a history of surgery was significantly higher in the H district than in the L district (58 versus 33.3%; P < 0.05). Of 20 patients infected with similar strains of HCV in the H district, 16 (80%) had at least one parenteral risk factor associated with medical care. These results indicate an increased transmission of similar strains of HCV in the H district as a result of nosocomial infection.