for Health Care Providers
Hepatitis C Genotypes and Quasispecies
Hepatitis C Virus Genotypes
An important variable for all patients with chronic hepatitis C virus (HCV) is the "genotype" of HCV with which they are infected. This is the strain of the virus to which they were exposed when they were infected, often many years prior to their evaluation, and it is determined by a simple blood test. Genotypes of HCV are genetically distinct groups of the virus that have arisen during its evolution.(1) Approximately 75% of Americans with HCV have genotype 1 of the virus (subtypes 1a or 1b), and 20-25% have genotypes 2 or 3, with small numbers of patients infected with genotypes 4, 5, or 6.(2) Most patients with HCV are found to have only one principal genotype, rather than multiple genotypes.(3, 4, 5) Genotype 4 is much more common in Africa than in many other parts of the world, genotype 6 is common in Southeast Asia, and each area of the world has its own distribution of genotypes.(6)
Clinical Significance of Hepatitis C Genotypes
Genotype generally has not been found in epidemiological studies to play a large role
in liver disease progression due to HCV. Rather, genotype is of clinical importance
principally as a factor in selecting the appropriate HCV medications for treatment. Please see the HCV Treatment Considerations
for more information.
- Bukh J, Miller R, Purcell R. Genetic heterogeneity of hepatitis C virus: quasispecies and genotypes. Semin Liver Dis 1995;15:41-63
- McHutchison JG, Gordon SC, Schiff ER, et al. Interferon alfa-2b alone or in combination with ribavirin as initial treatment for chronic hepatitis C . N Engl J Med 1998; 339:1485-1492.
- Manns MP, McHutchison JG, Gordon SC, et al. Peginterferon alfa-2b plus ribavirin compared with interferon alfa-2b plus ribavirin for initial treatment of chronic hepatitis C: a randomized trial. Lancet 2001; 358:958-965.
- Fried MW, Shiffman ML, Reddy R, et al. Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. N Engl J Med 2002; 347:975-982.
- Hadziyannis SJ, Sette H Jr, Morgan TR, et al. Peginterferon alpha-2a and ribavirin combination therapy in chronic hepatitis C: a randomized study of treatment duration and ribavirin dose. Ann Intern Med 2004; 140:346-355.
- Simmonds P. Genetic diversity and evolution of hepatitis C virus - 15 years on. J Gen Virol. 2004;85:3173-88.