Genotypes
Based on genetic differences between HCV isolates, the hepatitis C virus species is classified into seven genotypes (1-7) with several subtypes within each genotype (represented by lower-cased letters). Subtypes are further broken down into quasispecies based on their genetic diversity. Genotypes differ by 30-35% of the nucleotide sites over the complete genome. The difference in genomic composition of subtypes of a genotype is usually ~20-25%. Subtypes 1a and 1b are found worldwide and cause 60% of all cases.
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