What are the most common hepatitis C virus (HCV) genotypes?

Updated: Oct 07, 2019
  • Author: Vinod K Dhawan, MD, FACP, FRCPC, FIDSA; Chief Editor: BS Anand, MD  more...
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Answer

HCV genomic analysis by means of an arduous gene sequencing of many viruses has led to the division of HCV into six genotypes based on homology. Numerous subtypes have also been identified. Arabic numerals denote the genotype, and lower-case letters denote the subtypes for lesser homology within each genotype. [12]

Molecular differences between genotypes are relatively large, and they have a difference of at least 30% at the nucleotide level. The major HCV genotype worldwide is genotype 1, which accounts for 40%-80% of all isolates. Genotype 1 also may be associated with more severe liver disease and a higher risk of hepatocellular carcinoma. Genotypes 1a and 1b are prevalent in the United States, whereas in other countries, genotype 1a is less frequent. Genotype details are as follows:

  • Genotype 1a occurs in 50%-60% of patients in the United States.

  • Genotype 1b occurs in 15%-20% of patients in the United States; this type is most prevalent in Europe, Turkey, and Japan.

  • Genotype 1c occurs in less than 1% of patients in the United States.

  • Genotypes 2a, 2b, and 2c occur in 10%-15% of patients in the United States; these subtypes are widely distributed and are most responsive to medication.

  • Genotypes 3a and 3b occur in 4%-6% of patients in the United States; these subtypes are most prevalent in India, Pakistan, Thailand, Australia, and Scotland.

  • Genotype 4 occurs in less than 5% of patients in the United States; it is most prevalent in the Middle East and Africa.

  • Genotype 5 occurs in less than 5% of patients in the United States; it is most prevalent in South Africa.

  • Genotype 6 occurs in less than 5% of patients in the United States; it is most prevalent in Southeast Asia, particularly Hong Kong and Macao.

Within a region, a specific genotype may also be associated with a specific mode of transmission, such as genotype 3 among persons in Scotland who abuse injection drugs.


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