Genotyping of hepatitis B virus isolates from Lahaul and Spiti district in Himachal Pradesh, India.

Hepatitis B virus (HBV) has several genotypes. In the Indian population, genotypes A and D are the most frequent. HBV infection is hyper-endemic in the Lahaul and Spiti district in Himachal Pradesh; however, the virus genotype in this area is not known. We sequenced a 398-nucleotide segment of HBV genome that included parts of pre-S1/S2 and polymerase genes from 17 specimens from this district, and assigned a viral genotype to these. Of the 17 specimens studied, 13 (76% [95% confidence interval = 50-92%]) showed the presence of genotype C HBV; the remaining four were genotype D (n = 4; 24%) HBV. Prevalence of genotype C HBV was much higher in the district than in other parts of India. This may reflect the historical mixing of this population with that in China. Since genotype C has a higher risk of chronicity and mother-to-child transmission, prevention of HBV infection may need particular emphasis in this area.