G

• Genotype, HBV: There are 8 genotypes for HBV worldwide, labeled A through H, all of which have been found in the United States. Genotypes A and B are more responsive to interferon-based therapy compared with genotypes C or D, but initial responses to oral antiviral agents appear to be similar across genotypes.
• Gentoype, HCV: Hepatitis C viruses can be categorized into six major genotypes globally. Genotype 1 (subtypes 1a and 1b) is the most commonly isolated genotype in the United States, followed by 2 and 3. Genotypes 4, 5 and 6 are increasingly observed in the US, especially among foreign-born patients from Asia and Africa (see Map). Genotypes 1 and 4 HCV are associated with lower response rates to pegylated interferon and ribavirin compared with genotypes 2 and 3. Treatment responses to genotypes 5 and 6 are not as extensively described but thought to fall somewhere in between response rates of genotypes 1/4 and genotypes 2/3.