Characteristics of geographic distributions and route of infection for hepatitis B virus genotype D in Ehime area in western Japan

Aims: Hepatitis B virus genotype D (HBV/D) is rare in Japan, and has been shown to circulate in Ehime prefecture in western Japan. HBV/D is suspected to have been transferred into Ehime from Russia as a result of the Japanese–Russian War. This study examined the current geographic spread and infectious route for HBV/D in Ehime. Methods: HBV genotype was determined for 508 patients with chronic HBV infection and 46 patients with acute HBV infection hepatitis (acute hepatitis, AH), all of whom were living in Ehime. Ehime was divided into three areas and genotypic distributions were studied. Results: The ratio of genotypes A,B,C and D in chronically infected patients were 1.8%, 4.5%, 87.8% and 5.9%, respectively. Most patients chronically infected with HBV/D lived in the central area. Only two patients lived in the east and south-west areas, and both had lived in the central area in childhood. Patients with AH due to HBV/D were found only in the central area. Conclusion: HBV/D has not yet spread widely to areas other than central Ehime, although small numbers of infected people have moved to other areas. The major infectious route for patients with AH is sexual transmission, regardless of HBV genotype.