To date, eight HBV genotypes have been identified (A, B, C, D, E, F, G and H).1 The prevalence of the different genotypes varies with geographic location. Genotypes A and D are more common in Europe, Mediterranean regions and the US, whereas genotypes B and C are prevalent in Asia. The clinical relevance of genotype is not yet clearly defined, but the risk of liver disease may differ according to the infecting genotype. Liver disease may be more commonly associated with genotype C. Genotype C is also associated with a poor treatment outcome compared with genotype B.2 Genotype A may respond better to conventional interferon alfa (IFNα) therapy than non-A genotypes. Genotype D, which is highly prevalent in the Mediterranean area, is the genotype most likely to develop pre-core or basic core promoter mutations.

Overall, the precise role of viral genotype in disease pathogenesis and its effects on treatment outcome are yet to be elucidated.

1. Keeffe EB, Dieterich DT, Han SH, et al. A treatment algorithm for the management of chronic hepatitis B virus infection in the United States. Clin Gastroenterol Hepatol 2004;2(2):87-106.
2. Kao JH, Chen PJ, Lai MY, Chen DS. Genotypes and clinical phenotypes of hepatitis B virus in patients with chronic hepatitis B virus infection. J Clin Microbiol 2002;40(4):1207-9.

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