Hepatitis C Virus
HCV is the major etiologic agent of sporadic and transfusion-associated non-A, non-B hepatitis worldwide. Ca. 50% of all infections lead to chronic liver disease with varied clinical manifestations ranging from a largely asymptomatic carrier state to chronic active hepatitis, liver cirrhosis and hepatocellular carcinoma.
Geographic Pattern of HCV Prevalence
HCV is transmitted primarily via the parenteral route, but with the implementation of diagnostic tests to exclude HCV-contaminated blood products, the incidence of new HCV infections declined drastically.
Nevertheless, HCV is still an important medical problem, because about 170 million people are persistently infected with this virus and have a high risk to develop severe chronic liver disease such as liver cirrhosis and hepatocellular carcinoma.
Current therapy consists of the combination of a polyethylene glycol conjugated form of interferon-alpha and ribavirin. Sustained viral response is achieved in only about half of treated patients and combination therapy has serious side effects such as hemolytic anemia, severe depression and prolonged flu-like symptoms. These limitations of current treatment and the lack of a prophylactic vaccine underscore that more efforts are required for the development of efficient means to combat this insidious infection. In spite of a mild clinical course and a high proportion of asymptomatic cases, owing to the high rate of chronicity, HCV infections are a serious medical problem.
Based on sequence analyses HCV genomes can be grouped into at least 6 genotypes or 'clades' and multiple subtypes. In Western Europe and the United States, infections caused by genotypes 1a [the American prototype] and 1b [the Japanese prototype] are the most frequent ones, followed by infections with the genotypes 2 and 3. The other genotypes are very rare in these countries and can only be found in distinct geographical regions like Egypt (genotype 4), South Africa (genotype 5), and Southeast Asia (genotype 6).