Hepatitis C Genotypes

Hepatitis SA

Genotype Testing Genotyping is routinely performed prior to therapy. Genotype testing is covered by Medicare if you are considering treatment.

Genotype Distribution Globally, genotype 1 is most common, accounting for 46% of all infections, followed by genotypes 3 (22%), and genotypes 2 and 4 (13% each). There are significant variations across regions, with genotype 1 dominating in Australasia, Europe, Latin America and North America (53-71% of all cases) and genotype 3 accounting for 40% of all infections in Asia. Genotype 4 is most common (71%) in North Africa and the Middle East, but when figures from Egypt are excluded, it accounts for only 34% of infections, and genotype 1 accounts for 46% of infections.

In Australia, the predominant genotypes are genotype 1 (54%) and genotype 3 (37%) with genotype 2 accounting for around 5%.

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Hepatitis C Genotypes

Introduction

Quasispecies

Genotypes & Treatment

The hepatitis C virus (HCV) is an RNA virus related to the flavivirus family, which includes yellow fever, dengue fever, West Nile fever and Japanese encephalitis. RNA viruses are genetically less stable than DNA viruses, and are prone to mutate during replication. It’s a common misconception that hepatitis C is just one virus, but in reality (as a result of mutation over hundreds of years), it’s a group of very closely related strains. They are similar enough to be called HCV, but based on genetic differences, they can be classified into distinct groups called genotypes.

As the virus continues to replicate in each person, there is the potential for quasispecies to form. Quasispecies are very closely related mutations of the original virus with which the person was infected.

Over time, the diversity of quasispecies increases and may affect response to treatment.

Hepatitis C treatment regimes vary depending on the genotype of the virus you are living with. All direct-acting antiviral (DAA) drugs, the current preferred method of treatment, suppress ongoing HCV replication in the body, but different DAAs work better for different genotypes. Talk to your specialist or liver nurse to find out what treatment is best for your genotype. New medications targeting different genotypes are being developed all the time.

Already having Hepatitis C doesn’t protect you from reinfection. You can become infected with different strains and experience another acute stage of infection.

Similarly, if you have had hepatitis C and cleared the virus, you are not immune to being infected again later on.

Genotypes

Genotypes & Disease Progression While HCV genotype has been shown to be a major predictor of response to interferonbased antiviral therapy, in general it has not been thought to influence disease severity or the progression of liver disease.

The most commonly used classification scheme for HCV was established by Dr P. Simmonds. This system classifies hepatitis C into major genotypes, numbered 1, 2, 3, 4, etc.

Within the major genotype groups there are more closely related strains called subtypes.

These have been designated with lower-case letters, such as 1a, 1b, 1c, etc. There are at least six major genotypes (1-6) with many subtypes. Proposed types 7, 8, 9, 10 and 11 may be different to genotypes 1-6, or they may be subtypes of 1-6.

Modes of Transmission Genotyping can been used to study the ways hepatitis C is transmitted. It has been used to identify the source of infection in cases of patient-to-patient transmission, and is also useful in the study of other modes such as vertical transmission (mother to baby) and needle-stick injuries.

HCV image CC BruceBlaus (see http://bit.ly/293lEOt for more information)