Hepatitis C is an infectious disease affecting primarily the liver, caused by the hepatitis C virus (HCV). The infection is often asymptomatic, but chronic infection can lead to scarring of the liver and ultimately to cirrhosis, which is generally apparent after many years. In some cases, those with cirrhosis will go on to develop liver failure, liver cancer or life-threatening esophageal and gastric varices. HCV is spread primarily by blood-to-blood contact associated with intravenous drug use, poorly sterilized medical equipment and transfusions. An estimated 130Ã±170 million people worldwide are infected with hepatitis C. The existence of hepatitis C (originally “non-A non-B hepatitis”) was postulated in the 1970s and proven in 1989.It is not known to cause disease in other animals. The virus persists in the liver in about 85% of those infected. This persistent infection can be treated with medication; peginterferon and ribavirin are the current standard therapy. Overall, between 50Ã±80% of people treated are cured. Those who develop cirrhosis or liver cancer may require a liver transplant. Hepatitis C is the leading cause of liver transplantation though the virus usually recurs after transplantation. No vaccine against hepatitis C is currently available.