Hepatitis C is caused by the hepatitis C virus that was discovered in 1989. Humans are the only reservoir of hepatitis C virus. The infection is mainly acquired through contact through broken skin with infectious blood (often through sharing contaminated equipment among injecting drug users). The risk of mother-to-child transmission is around 3–5%, but in cases of simultaneous HIV infection it may reach 15%. Sexual transmission seems to be infrequent. After 1991, blood transfusions and blood products became much safer than before, as routine HCV tests started to become widely available.

Vaccination against hepatitis C is not yet available. The disease burden of hepatitis C is high, with up to 170 million people estimated to have had contact with the virus and 130 million people chronically infected worldwide. Hepatitis C is considered to be the leading cause of liver cancer and liver transplants in Europe and the USA. The most effective preventive measures are screening and testing of blood and organ donors, virus-inactivating processing of blood products, good infection control and safe injection practices in healthcare settings.