Hepatitis C is an infectious disease primarily affecting 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 or other complications, including liver cancer or life-threatening esophageal varices and gastric varices. The hepatitis C virus is spread by blood-to-blood contact. Most people have few, if any, symptoms after the initial infection, yet the virus persists in the liver in about 85% of those infected. Persistent infection can be treated with medication; peginterferon and ribavirin are the current standard therapy. Overall, between 51-80% of treated patients are cured. Those who develop cirrhosis or liver cancer may require a liver transplant, and the virus universally recurs after transplantation.
An estimated 180 million people worldwide are infected with hepatitis C. Hepatitis C is not known to cause disease in other animals. No vaccine against hepatitis C is currently available. The existence of hepatitis C (originally "non-A non-B hepatitis") was postulated in the 1970s and proven in 1989.