HEPATITIS-C VIRUS GENOTYPES - EPIDEMIOLOG Y, DIAGNOSIS AND CLINICAL IMPLICATIONS

Hepatitis C virus demonstrates a high degree of variability HCV isolat es have been classified into at least six genotypes, according to the percentage of nucleotide sequence homology. Geographical differences i n he distribution of virus genotypes are well documented. Types 1, 2 a nd 3 are the major types observed in Japan, Western Europe and North A merica; type 4 has been found in Central and Northern Africa and in th e Middle East type 5 has been described in South Africa, type 6 in Sou th-East Asia. The relative prevalence of these genotypes varies betwee n different regions: in the Indian subcontinent subtype 1b seems to be the most prevalent type, but many isolates have been described, relat ed to genotype 3, in Northern and Southern India, Pakistan and Nepal. HCV genotypes may have potential clinical implications: a) the associa tion with the severity of liver disease is still controversial; b) the association between some genotypes, particularly 1b, and a poor respo nse to interferon alpha therapy has been well established; c) genotypi ng may be useful for identifying some unusual modes of transmission of the virus. Finally, the variability of HCV virus has major implicatio ns for the design of new vaccines strategies since there is no cross-p rotection between different HCV types.