Hepatitis means inflammation of the liver. Alcohol, prescription and nonprescription drugs, autoimmune diseases and fat accumulation in the liver can all cause hepatitis. However, viruses are the main causes of the disease. The most common culprits in the United States are hepatitis A virus (HAV), hepatitis B virus (HBV) and hepatitis C virus (HCV).

HAV is usually spread by putting something in the mouth that has been contaminated with traces of feces from a person with hep A. HBV is commonly transmitted by sex, contact with blood or via childbirth. HCV is most easily spread through direct blood-to-blood contact. Common HCV routes include shared needles and other equipment used to inject drugs, as well as via blood transfusions and organ transplants that were performed before July 1992.