Prevalence and Treatment of Hepatitis C Virus Genotypes 4, 5, and 6

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Infection with hepatitis C virus (HCV) genotypes 4–6 (with the previously named genotypes 7–9 included as subtypes of genotype 6) is distributed and studied less widely than genotypes 1–3. However, genotypes 4–6 are very common in geographic areas where chronic hepatitis C is highly prevalent. In fact, the majority (87%) of the 169.7 million HCV-infected individuals worldwide are from western Pacific countries (62.2 million), southeast Asia (32.3 million), Africa (31.9 million), and eastern Mediterranean countries (21.3 million). It is among this large population outside of the Americas and Europe that these less well known genotypes are found: genotype 4 in Egypt and Africa, genotype 5 in South Africa, and genotype 6 in southeast Asia. The existing literature, although limited, suggests that patients with chronic hepatitis C genotypes 4–6 may exhibit different clinical courses and treatment outcomes. Ethnicity-related factors may contribute to the presence of more advanced disease in patients with genotype 4, who also tend to have a poor response to interferon-based therapy. HCV genotype 5 appears to be an easy-to-treat virus with response rates similar to those of genotypes 2 and 3 after a 48-week course of therapy. Response to treatment in patients with HCV genotype 6 may be at an intermediate level between that seen with genotype 1 and genotype 2 or 3. The optimal duration of treatment (24 vs 48 wk) for HCV genotype 6 is unclear and currently is under investigation.

Section snippets

Classification and Diagnosis of Novel Hepatitis C Virus Genotypes

Although HCV genotypes 4 and 5 can be diagnosed reliably by most commercially available assays for HCV genotyping (Table 1), the diagnosis of certain subtypes of genotype 6 (the so-called novel genotypes 7–9) can be a challenge using similar diagnostic assays. Genotypes 7–9 are related closely to genotype 6 and recently have been reclassified as subtypes of genotype 6 by the Los Alamos National Laboratories (Table 2).4 HCV genotypes 7–9 share significant homology with genotype 1 in the highly

Hepatitis C Virus Genotype 4

HCV genotype 4 is encountered throughout Africa and eastern Mediterranean countries, and usually among immigrants or indigenous injection drug users in North America and Europe.7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18

Egypt has the highest HCV genotype 4 prevalence of 91% according to a survey of 122 HCV-infected patients from 15 regions of the country.7 Saudi Arabia probably has the second highest HCV genotype 4 prevalence (60%).10 The prevalence for HCV genotype 4 varies between 11% and 75%

Hepatitis C Virus Genotype 5

HCV genotype 5 is the predominant genotype in South Africa.41 A study of 130 HCV-infected individuals (blood donors, chronic renal failure patients, adult outpatients, and hemophiliacs) from 3 regions of South Africa reported a prevalence of 39.2% for genotype 5, 33% for genotype 1, 21.5% for genotypes 2 and 3, and only 2.3% for genotype 4. Although relatively restricted to South Africa, HCV genotype 5 also can be seen in ethnically diverse European regions such as the Benelux countries.42 Most

Hepatitis C Virus Genotype 6

HCV genotype 6 and 6 subtypes (previously known as genotypes 7–9) have been found primarily in south China, Hong Kong, Taiwan, Macao, and southeast Asia including Singapore, Malaysia, Vietnam, Thailand, and Burma.2, 49, 50, 51, 52, 53, 54 HCV genotype 10a and 11a also have been found in southeast Asia, but only from Indonesia to date.55 HCV genotype 10a is considered a divergent subtype of genotype 3 (3k), but genotype 11a is related closely to genotype 6 and is considered a subtype of genotype

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    Dr Keeffe has received research funding from and has been a consultant for Roche.

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