What Are Hepatitis C Genotypes?

Question: What Are Hepatitis C Genotypes?

Answer: The hepatitis C virus (HCV) has at least six distinct genotypes, which are just different sequences of the virus's DNA, which are identified by a number. These six genotype sequences are enough alike to be a hepatitis C virus, but have enough small differences between them to be organized into six different groups. In addition to genotypes, there are over 50 subtypes within those genotypes, which are identified by a lowercase letter. These different "strains" of hepatitis C virus result from the high chance of mutation in its genetic code when it replicates. Over the years very similar, but technically different, types of hepatitis C virus develop. Regardless of the type of HCV, they all cause the same disease -- hepatitis C. In the United States, about 57% of people with hepatitis C have genotype 1a, which is the most common type. Genotype 1b is in about 17% of people. Genotypes 2 and 3 are the next most common.

It is certainly possible to be tested to find out which genotype you have, and it's actually a good idea to find out because different types best respond to different treatment. For example, genotype 1 is generally more difficult to treat and people with this genotype have less than a 50% chance of clearing the hepatitis C virus. However, people with genotype 2 or 3 have greater than a 50% chance of clearing the virus. Those who have these genotypes respond up to 2 times better with Interferon and Ribavirin therapy than those with genotype 1 infection.

Another interesting part of genotypes is that they seem to be distributed geographically. Genotype 1a is most common in the United States, but genotype 1b is most common in Europe. Genotype 4 is most common in the Middle East.

_Sources:

Berenguer M, Wright TL. Hepatitis C. In: M Feldman, LS Friedman, LJ Brandt (eds), Gastrointestinal and Liver Disease, 8e. Philadelphia, Elsevier, 2006. 1684.

Massachusetts Department of Public Health. 2002. Hepatitis C Testing and Diagnosis.

US Department of Verterans Affairs. February 2, 2007. Understanding Lab Tests.