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Hepatitis C Genotypes

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Updated October 20, 2009

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There are at least 6 genotypes -- genetic strains -- of hepatitis C virus. Knowing your hepatitis C genotype is an essential part of your treatment plan because the genotype will affect your treatment, such as how long you're treated. Since finding your genotype requires a specialized blood test, your blood will be taken at your doctor's office or clinic but sent to an outside lab for testing.

Genotype 1

Genotype 1 is the most common hepatitis C genotype in the United States and Europe. Approximately 80 percent of hepatitis C infections in the U.S. are genotype 1. If you have this genotype, and need treatment, you will usually be treated with peginterferon and ribavirin for 48 weeks. However, the SVR rate (What is SVR?) is less than 50 percent, which means that less than half of the people will have an undetectable viral load six months after treatment ends. If you don't have a significant drop in viral load after 12 weeks of treatment, your doctor may discontinue treatment and try other options.

Genotype 2

Genotype 2 is the second most common hepatitis C genotype in the United States (about 10 percent are infected with this type). If you have this genotype, you will have an 80 percent chance of achieving SVR with standard therapy. Treatment for this genotype is shorter in duration and usually requires a smaller dose of ribavirin. Currently, treatment is a combination of peginterferon and ribavirin taken for 24 weeks. Some studies suggest it's possible to successfully treat people with this genotype in less than 16 weeks.

Genotype 3

This genotype is endemic in southeast Asia, but unevenly distributed throughout India, the Far East and Australia. It's estimated that about 6 percent of Americans have genotype 3. Treatment is very similar to treating genotype 2 infections. Likewise, the chance of achieving SVR is similar.

Genotype 4

This genotype is most common in Africa, the Middle East and several eastern European countries. Egypt has an especially high number of people infected with hepatitis C virus genotype 4. Treatment is the same as genotype 1: A combination of peginterferon and ribavirin taken for 48 weeks.

Genotype 5

This genotype is common in infections from South Africa. Treatment is the standard 48-week combination therapy and seems to have SVR rates comparable to genotypes 2 and 3.

Genotype 6

This genotype is common in south China, Hong Kong and other southeast Asian countries. Studies will eventually determine the best treatment guidelines for genotype 6, but current research suggests that a combination therapy of 48 weeks leads to a SVR rate between 50 and 80 percent.

Variations in Treatment

Your specific type of hepatitis C infection won't necessarily respond in the ways described above because many factors affect treatment. Some examples include:
  • If you are coinfected with the hepatitis B virus
  • If you are coinfected with HIV
  • If you are immunocompromised because of an infection or treatment
  • If you have decompensated cirrhosis
  • If you have had a liver transplant
  • If you have certain complications to chronic hepatitis C
  • If you've relapsed or previously not responded to treatment
  • If you're African-American or Hispanic (In general, African-Americans and Latinos will have a lower SVR rate to interferon-based treatment than non-Latino Caucasians.)

Genotypes Beyond

Though only six genotypes are discussed here, there are others that currently play a lesser role in hepatitis C infections. However, as the hepatitis C viruses evolve and world populations migrate, these major genotypes may change, too. The major commercial labs usually only identify the six major genotypes. Other types will probably be treated, at least initially, using the same strategies for genotype 1.

Sources:

Chopra, S. Treatment of Chronic Hepatitis C Virus Infection: Recommendations for Adults. UpToDate. Waltham, MA. Accessed: October 14, 2009.

Di Bisceglie, A. Pegylated Interferon in the Treatment of Chronic Hepatitis C Virus Infection. UpToDate. Waltham, MA. Accessed: October 14, 2009.

Dienstag, JL. Acute Viral Hepatitis. In: AS Fauci, E Braunwald, DL Kasper, SL Hauser, DL Longo, JL Jameson, J Loscaizo (eds), Harrison’s Principles of Internal Medicine, 17e. New York, McGraw-Hill, 2008.

National Digestive Diseases Information Clearinghouse. Chronic Hepatitis C: Current Disease Management. Accessed October 11, 2009.

United States Department of Veterans Affairs. Hepatitis C Genotype. Accessed October 15, 2009.

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