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The Hepatitis C virus is a member of the virus family Flaviviridae and is unique in this family because its primary mode of transmission is not through mosquitoes like other flaviviruses.
The virus usually takes a long time to cause damage and can take 20 to 40 years to kill an individual.
The virus is mainly spread through parenteral or percutaneous transmission. The virus enters a new host through needle inoculation, blood transfusion, or sexual contact in which there is breakage of percutaneous barriers. 4 million people in the United States are infected with Hepatitis C virus and a minimum estimate of 100 million people are infected worldwide. There are 6 strains (genotypes) of HCV and more than 50 subtypes have been identified.
Symptomatology and outcome
The virus, after gaining entry in the host, travels through the blood stream and eventually attacks the hepatocytes, probably using a yet unidentified surface molecule to attach and gain entry. Hepatitis C differs from other forms of hepatitis because it is more likely to remain clinically inapparent. Close to 80% of patients that are infected with HCV go on to develop chronic infection in the liver. This disease attacks the liver and studies have shown that 30 to 46% of patients develop cirrhosis, 11 to 19% develop hepatocellular carcinoma, and a high rate of liver-related death. However, scientists do not fully understand why the human immune response is unable to defend the body. HCV has been shown to have a high mutation rate in the hypervariable region of the envelope protein. This means that as HCV changes in the body, the antibodies released by the humoral immune system are unable to bind to the new mutant or if they do bind then they are unable to inactivate the virus. Also, HCV has been shown to elicit a weak T-cell response from the cellular immune system. Scientist do not understand why HCV can have such a small immune response in individuals who have a normal immune response to other viruses. The puzzle is beginning to come together as new evidence reveals that several HCV proteins, such as core, E2, and NS5A, interfere with the immune response.
Prevention and management
Because of the inability to launch an effective immune response to HCV, no vaccine has been produced and scientists are having difficulties in coming up with models to test vaccine ideas.