Hepatitis: Inflammation of the liver from any cause.
Hepatitis is most often viral, due to infection with one of the hepatitis viruses (A, B, C, D, and E) or another virus (such as those that cause infectious mononucleosis, cytomegalovirus disease, or yellow fever). The main nonviral causes of hepatitis are alcohol and drugs.
Hepatitis is a major public health problem. Approximately 400 million people have hepatitis B and 170 million have hepatitis C. Both cause chronic liver infection that can be fatal. Hepatitis B and C are implicated in 80% of cases of liver cancer, the fourth leading cause of cancer deaths in the world.