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Gastroenterol. 2009 Dec 14;15(46):5761-9.    Ten hepatitis B
virus (HBV) genotypes (A-J) and 34 HBV subgenotypes have been
identified so far. HBV genotypes and subgenotypes have distinct
geographical distributions, and have been shown to differ with
regard to clinical outcome, prognosis, and response to
interferon treatment. Infection with subgenotype A2 is
frequently associated with high viral load, resulting in acute
infection via horizontal transmission. Genotypes A and B are
more sensitive to interferon treatment than genotypes D and C,
respectively. Genotype B is more frequent in acute hepatitis
than genotype C, whereas genotype C (C2) is more frequently
associated with an increased risk of hepatocellular carcinoma
(HCC), mostly cirrhotic, as compared with genotype B (B2).
Genotype mixture is associated with high viral load and worse
outcome of HBV infection. HBV mutations in the S genes,
especially amino acids substitution at position 145 (G145R),