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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.
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.
Division
of Gastroenterology and Hepatology, Department of Medicine,
Stanford University
Medical Center,
Palo Alto, California.
10/20/05
Reference
M
H Nguyen and E B Keefe. Prevalence and treatment of hepatitis
C virus genotypes
4, 5, and 6. Clinical Gastroenterology and Hepatology
3: Suppl 2:97-101.
October 2005.
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