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What is a "Hepatitis C Genotype" and why is it important?

Medically reviewed by Sally Chao, MD. Last updated on Sep 1, 2021.

Official answer

by Drugs.com

A genotype is a strain or form of a virus. Hepatitis C has at least 7 identified genotypes. It is important to know the genotype of hepatitis C before starting treatment. The genotype variations will affect which drugs are used to treat the virus and for how long.

The genotype is the strain of hepatitis C a person was exposed to when they became infected. The genotype can be learned from a blood test. Different genotypes arise over time as a virus develops and changes. Different parts of the world tend to have different genotypes. In the United States, the most common genotypes are types 1, 2 and 3. Genotype 4 is more common in Africa. Genotype 6 is most common in Southeast Asia.

All of the genotypes of hepatitis C can be treated, but the drug to use and the length of time to treat may change depending on the genotype. Everyone diagnosed with hepatitis C should be tested for the genotype before treatment. Untreated hepatitis C can cause liver damage or liver cancer. The genotype does not seem to affect how likely the infection is to cause liver damage.

Each genotype of hepatitis C may have several subtypes. So far, more than 80 subtypes of hepatitis C have been identified. Another reason the genotypes and subtypes are significant is that the diversity has made it harder to develop a vaccine for hepatitis C. Researchers have been trying for many years to develop a vaccine that will be effective for the different genotypes and subtypes.

Diagnosing hepatitis C

There are three important blood tests for diagnosing hepatitis C:

  • The first is a blood test for antibodies to the virus. If you have antibodies, it means you have been exposed to hepatitis C at some time. It does not mean you have an active infection. Some people are exposed to hepatitis C, but their immune system fights it off. This is called acute hepatitis C.
  • If you have positive antibodies, the next test will be a blood test to look for genetic material from the virus called C RNA. The presence of C RNA means the virus is active in your body. The more C RNA you have, the more active the infection.
  • The final test is for the genotype in order to plan treatment. As you respond to treatment, blood tests will be done to see if C RNA levels will start to fall.

Medications called direct-acting antiviral medicines were developed in 2013. These medications can cure most cases of hepatitis C, no matter what the genotype is. Treatment may last between 8 to 24 weeks, depending on the genotype you have.

References
  1. U.S. Department of Veterans Affairs. Genotypes Hepatitis C. October 2018. Available at: https://www.hepatitis.va.gov/hcv/background/genotypes.asp. [Accessed August 12, 2021].
  2. Centers for Disease Control and Prevention (CDC). Viral Hepatitis. August 2020. Available at: https://www.cdc.gov/hepatitis/hcv/hcvfaq.htm. [Accessed August 12, 2021].
  3. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Hepatitis C. March 2020. Available at: https://www.niddk.nih.gov/health-information/liver-disease/viral-hepatitis/hepatitis-c. [Accessed August 10, 2021].
  4. Hedskog C, Parhy B, Chang S, et al. Identification of 19 Novel Hepatitis C Virus Subtypes—Further Expanding HCV Classification. Open Forum Infectious Diseases. Volume 6, Issue 3, March 2019, ofz076. https://doi.org/10.1093/ofid/ofz076.
  5. Bailey JR, Barnes E, Cox AL. Approaches, Progress, and Challenges to Hepatitis C Vaccine Development. Gastroenterology. 2019 Jan;156(2):418-430. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6340767/.

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