Hepatitis C is a liver disease caused by the hepatitis C virus, which is usually spread through contact with infected blood. The virus can cause both acute and chronic hepatitis and, while most people clear the virus spontaneously, 60-70% of people who become infected develop a chronic infection. Chronic hepatitis C can lead to serious liver problems, including cirrhosis or liver cancer, so it's important for those at risk to get tested and seek medical help if infected.