Understanding Hepatitis C Genotypes

Rapid Spread of Hepatitis C Infections Accounts for Broad Genetic Variation

Hepatitis C

There are currently 11 different genetic strains (genotypes) of hepatitis C virus (HCV) in the world, although the highest prevalence is seen with genotypes 1 through 7. In addition to this, each genotype can be further broken down into specific subtypes, which are classified numerically (e.g., HCV genotype 1a or 1b).

Genotyping is considered vital as it helps doctors determine which drugs will work most effectively for your specific virus (or viruses if you are infected with more than one HCV genotype).

The process of identification requires nothing more than a simple blood test, the sample of which is analyzed using a technology known as a polymerase chain reaction (PCR) assay.

Genotype 1

Genotype 1 is the most common HCV genotype in North America and Europe and accounts for nearly 80% of all infections in the U.S. Genotype 1 infections are considered among the most difficult to treat, although newer direct-acting antivirals (DAAs) are achieving higher cure rates in both newly treated and previously treated patients. HCV genotype 1 can be further broken down into subtypes 1a, 1b, and 1c.

Genotype 2

Genotype 2 is the second most common HCV genotype in the U.S., accounting for about 10% of all infection. Prior to the introduction of DAAs, it was one of the more easily treated genotypes, with patients having 80% chance of achieving a sustained viral response (SVR) consistent with a cure. Today, that figure is closer 90% in many previously treated patients and as high as 99% in newly treated patients.

Genotype 2 also has three main subtypes: 2a, 2b, and 2c.

Genotype 3

Genotype 3 is endemic to southeast Asia and unevenly distributed throughout Australia, India and other parts of the Far East. It's estimated that about 6% of Americans have HCV genotype 3, which can break down into two main subtypes: 3a and 3b.

Genotype 4

Genotype 4 is most common in Africa, the Middle East, and several eastern European countries. Egypt has an especially high number of people infected with genotype 4, as well as the largest HCV population in the world. The high rate of HCV infections in these regions accounts, in large part, for the virus' broad genetic diversity, which include subtypes 4a, 4b, 4c, 4d, and 4e. 

Genotype 5

Genotype 5 is most commonly seen in southern Africa and is considered to have a little genetic variation with one main subtype: 5a.

Genotype 6

Genotype 5 is common in southern China, Hong Kong, and other southeast Asian countries. Like genotype 5, there is one main subtype: 6a. 

Genotype 7

Genotype 7 was added to public databases in 2014 and has thus far been identified in Thailand and the Democratic Republic of Congo. It has one main subtype: 7a.

In addition, genotypes 9, 10 and 11 have been identified, although infections have been relatively isolated within Vietnam and parts of Indonesia.

HCV Treatment by Genotype

With the advent of direct-acting antivirals, patients have an expanding range of HCV treatment options. Currently, the U.S. Food and Drug Administration has approved the following DAAs for use in patients with HCV genotypes 1-4 and 6:


Rockstruh, J. "Summary from EASL 2015 for Hepatitis C All oral HCV DAA therapy on its way to optimization: still much to learn." 50th Meeting of the European Association for the Study of the Liver (EASL). April 22-26, 2015; Vienna, Austria.

National Digestive Diseases Information Clearinghouse. "Chronic Hepatitis C: Current Disease Management." 

U.S. Department of Veterans Affairs. "Hepatitis C Genotype."