Six major strains (genotypes) of the hepatitis C virus (HCV) cause infection. You may be infected with more than one genotype at a time.
- Genotype 1 is the most common strain in the United States.
- Genotypes 1, 2, and 3 are found worldwide.
- Genotype 4 is found throughout northern Africa.
- Genotype 5 commonly is found in South Africa.
- Genotype 6 is common in Asia.
Genotype testing is done with a blood test.
How genotype affects treatment
Although genotype tests are not used to diagnose HCV infection, they may be done before treatment begins. Knowing the genotype may help a doctor choose the best treatment plan. You should know your genotype before treatment starts.
The antiviral medicines peginterferon and ribavirin are more likely to work for people who have genotype 2 or 3. These medicines also are used to treat people who have genotypes 5 and 6.
If blood tests show that you have responded to antiviral therapy (the virus is not detected in your blood) after 6 months, treatment may be:
- Continued for another 6 months, if you are infected with genotype 1.
- Stopped, if you are infected with genotype 2 or 3. Prolonging treatment does not seem to provide any more benefit.