Hepatitis C virus genotyping: clinical implications and methods.

Hepatitis C virus (HCV) chronically infects at least 1% of the world's population and is a leading cause of end-stage liver disease. HCV displays a remarkable degree of genomic diversity, with the six major genotypes and numerous subtypes differing in geographic distribution. The ability of this virus to cause persistent infections is a direct result of its genomic plasticity and the evolution of quasispecies within an infected individual. HCV genotype has emerged as an important factor both in predicting a sustained response to, and in determining the duration of, antiviral therapy. Although a variety of methods have been used for genotyping HCV, nucleotide sequencing of a phylogenetically informative region remains the gold standard.