Hepatitis C genotypes, explained

Infection with the hepatitis C virus (HCV) causes inflammation in the liver. Over time, the infection can result in significant damage and scarring to the liver. It often causes no noticeable symptoms, however, and a person can have HCV and not know they have it.

If you’ve read or talked to a healthcare provider about HCV, you’ve probably come across the term genotype. In reference to HCV, genotypes are different versions of the HCV virus. There are seven major genotypes found throughout the world, called genotypes 1 through 7. These are further classified by subtypes, which are labeled with letters—a, b, c, d, and so on.

Categorizing HCV by genotype helps healthcare experts understand the disease at a global scale. About 50 million people worldwide have chronic HCV, according to the World Health Organization.

Knowing the genotype of an HCV infection is also important to healthcare providers and patients, because different HCV genotypes respond differently to certain treatments.

What causes different genotypes of HCV?

Viruses evolve, just like any other living organism. As HCV has replicated an incalculable number of times—there have been hundreds of millions of cases throughout the decades, and the virus can replicate inside the body trillions of times in a single day—new genetic traits emerge, due to mutation, errors in RNA, and adaptation. Over time, different genotypes emerge.

How do you know your hep c genotype?

Hepatitis C is diagnosed through a series of blood tests. The initial screening is an HCV antibody test that will show whether you have ever had the infection. In 20 to 40 percent of people who contract HCV, the virus clears without leading to a chronic infection. If the antibody test is positive, a follow-up test will confirm whether an HCV infection is active. If the infection is active, additional testing will be used to determine the viral load and genotype.

Are some genotypes more common than others?

Overall, genotype 1 (which includes subtypes 1a and 1b) is the most common HCV genotype worldwide, as well as the most common in the United States. However, different genotypes are more common in different parts of the globe. For example, genotype 3 is the most common genotype in Southeast Asia, Australia, Africa, and the Middle East.

How does the genotype impact treatment?

There are numerous medications available for HCV treatment. Specific medications are better for certain genotypes, though some treatments are effective at treating multiple genotypes. Treatment typically involves a course of one or more medications taken over several months.

However, genotype is only one factor that must be considered when deciding on HCV treatment. The health of the liver, overall health, other medical conditions, pregnancy, and previous treatments are other factors that a healthcare provider will take into account when deciding on a course of treatment.