Prevalence and treatment of hepatitis C virus genotypes 4, 5, and 6.

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.