Hepatitis C

Hepatitis C is a liver disease caused by the hepatitis C virus (HCV). Hepatitis C virus is one of the viruses (A, B, C, D, and E), which together account for the vast majority of cases of viral hepatitis all of which can attack and damage the liver. Widely viewed as one of the most serious of the five, the hepatitis C virus is spread primarily through contact with infected blood and can cause cirrhosis (irreversible and potentially fatal liver scarring), liver cancer, or liver failure.

HCV is a small, enveloped, single-stranded RNA virus of the family Flaviviridae which appears to have a narrow host range. Humans and chimpanzees are the only known species susceptible to infection, with both species developing similar disease. HCV is also organ specific. It only replicates in liver cells although it may be found in others.

The hepatitis C virus replicates inside its host every 7 to 9 hours and typically produces about 1 trillion viral copies per day. Because the virus mutates rapidly, changes in the envelope protein may help it evade the immune system, which in turn is probably related to the high propensity (80%) of inducing chronic infection. There are at least 6 major genotypes and more than 50 subtypes of HCV. The different genotypes have different geographic distributions. Genotypes 1a and 1b are the most common in North America and Europe. Genotypes 2 and 3 are present in only 10 to 20 percent of patients. There is little difference in the severity of disease or outcome of patients infected with different genotypes. However, patients with genotypes 2 and 3 are more likely to respond to alpha interferon treatment.

Globally, an estimated 170 million persons are chronically infected with HCV and 3 to 4 million persons are newly infected each year.