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Hepatitis C Virus Genotypes
Last reviewed: 23.04.2024
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There are 6 genotypes and 11 major subtypes of the hepatitis C virus. Genotype 1, especially 1b, causes a more severe course of the disease and is most resistant to treatment. In this case, a higher level of viremia is usually recorded. On the basis of genetic heterogeneity of HCV strains, it was suggested that the divergence of genotypes of the hepatitis C virus occurred approximately 300 years ago.
[The prevalence of genotypes of the hepatitis C virus in the world
HCV genotypes are distributed unevenly. So, genotypes 1, 2, 3 are common everywhere. Genotypes 1 and 2 predominate in Western Europe and the Far East (with the exception of Thailand). Genotypes 1a and 1b are most common in the USA, whereas 2a, 2b, 3a are rare. Genotype 4 is common in Africa, and in Egypt and Zaire is dominant, in South Africa, genotype 5 prevails. Genotype 6 is most often found in Asia. In Japan, genotype 1a occurs in 1%, 1b in 74, 2a in 18, 2b in 6% of patients with chronic hepatitis C, co-infection 1b + 2a in 1% of them.
The distribution of genotypes of hepatitis C virus among patients with somatic pathology (hemophilia, hemoblastoses, malignant solid tumors), patients of hemodialysis departments, etc. Is largely determined by the area of residence - most are patients with the HCV genotype, the most common in this region. However, at present, given the wide international connections, this situation may change in some regions.
The predominant genotype of the hepatitis C virus in Japan is 1b. However, Japanese patients with hemophilia annually receive a significant number of blood products from the United States, where the genotype 1a remains predominant at the moment. By 1996, more than one-third of HCV-infected hemophiliacs in Japan had genotype 1a, while in the Japanese population as a whole, its prevalence barely exceeded 1% of all HCV-infected people.
In hematological adult patients, the genotype 1b prevails in Russia (51.8% of cases), then genotypes 3a - 22.8%, 1a - 3.6%, 2 - 2.4%, a mixture of genotypes - 1 , 2%; untyped - 18.1%; in the group of chronic HCV nos: 1b - 63.2%, 3a - 21%, 1a - 0%, 2 - 5.3%, non-typed - 10.5%, the mixture of genotypes is not detected.
The total distribution of genotypes of hepatitis C virus in 2006 was as follows: in the group of hematological patients: 1b - 35.6%, 3a - 22%, 1a - 4%, 2 - 5.9%, mixture of genotypes - 5.3%; non-typed - 27,2%, in patients without hematological pathology: 1b - 33,3%, 3а - 32,05%, 1а - 2,6%, 2 - 10,25%, mixture of genotypes - 5,1%; untyped - 16.7%. Both groups of patients are characterized by a 1.5-fold decrease in the percentage of genotype Ib in comparison with 2003. Data for 2004-2006. By percentage of genotypes for a group of hematological patients show: the proportion of genotype 3a has not changed; 2 - gradually increased from 2.4 to 8.35%; 1a - after a twofold increase in 2004, it decreased to 2.5% by 2006, and by 2006 there was a marked increase in the share of the mixture of genotypes - up to 8.35%, while in the majority of the mixtures genotype 1a was present. Data for 2004-2006, in the second group, the proportion of genotype Za increases from 21 to 42%; genotype 2 - sharply increases to 17.2% in 2004 and gradually decreases to 3.3%; The low level of genotype 1a (3-4%) was kept. Both groups of patients are characterized by a significant increase (up to 30%) in the proportion of untyped HCV variants in 2005 and a decrease in 2006
There is a relationship between the genotype of the hepatitis C virus and the pathway of infection. Genotype 1b is found in more than 80% of HCV-infected patients who received blood products, whereas in HCV-infected drug users it is detected only in isolated cases, and their genotype 3a prevails.
The most commonly identified among Russian children with chronic hepatitis C, occurring against a background of severe somatic pathology, is genotype 1b, detected in more than 25%. Genotypes 5 and 6 were not detected. Genotype 1a was found in 9.6%, 2a in 12.2%, 2b and 3a in 9.6%, 3b in 6.1%, and 4 in 18.2% of children.
The blood serum of 8.6% of patients is positive simultaneously with respect to two genotypes. Although the geiagit C virus is largely capable of mutations, given that the nucleotide sequences of the conserved sections of the HCV genome were used to create primers for genotyping, the detection of several genotypes in one patient may indicate a repeated infection with its hepatitis C virus during the treatment of a physical disease.
In general, the distribution of HCV genotypes in children with somatic pathology is not fundamentally different from the prevalence of HCV genotypes both in the European Region and in Russian children with a non-aggravated premorbid background.
When comparing the prevalence of genotypes of the hepatitis C virus among children with different somatic pathologies, no statistically significant differences were revealed. Apparently, both the presence of a common donor blood bank and the formation of "horizontal" transmission routes in the somatic hospital play a role here.