[Hepatitis C virus. Structure and genetic variability].

Infection by hepatitis C virus is characterized by a high rate of chronicity and low viremia. The virus has only been recently identified; it is a positively stranded RNA virus which shows homology in its genetic organisation with the Pestiviruses and Flaviviruses. There is not yet efficient culture system available. Several evidences indicate that the genetic variability of HCV genome might have important clinical implications; in particular infection by genotype 1b is less responsive to interferon treatment and, possibly, associated to more severe liver diseases.