Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Hepatitis is inflammation of the liver. There are several types of hepatitis. The disease has several causes.

One cause of hepatitis is infection. Most cases of infectious hepatitis in the United States are caused by hepatitis A, B or C virus.

An infection with one of these viruses might not cause any symptoms. Or it might cause only a mild, flu-like illness. Hepatitis A is usually a mild short-term illness. But hepatitis B and C often cause long-term (chronic) infections.

Hepatitis D is uncommon. Hepatitis E occurs primarily in underdeveloped countries.

Depending on the hepatitis virus, the infection can be spread in a number of ways. These include:

  • Contact with the stool of an infected person (A)

  • Eating shellfish from waters contaminated with sewage (A)

  • Contact with the blood, vaginal fluids, semen or breast milk of an infected person (B)

  • Unprotected sex (B and C)

  • Sharing contaminated needles (B, C and D)

Improved blood screening techniques have greatly reduced the risk of catching hepatitis B or C from blood transfusions.

Hepatitis has many other possible causes. These include:

  • Alcohol consumption at high levels. This is a common cause of hepatitis in the United States. .

  • Medications, especially high dose acetaminophen (Tylenol). Many other drugs also can cause liver inflammation.

  • Other viruses besides the hepatitis viruses, such as Epstein-Barr virus (the most common cause of mononucleosis)

  • Some bacteria, fungi and parasites

  • Your immune system. In autoimmune hepatitis, your body attacks its own liver cells.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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