Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Hepatitis is inflammation of the liver. Hepatitis B is hepatitis caused by the hepatitis B virus.

Hepatitis B virus spreads through contact with infected blood. Specifically, hepatitis B may be spread through:

  • Direct contact with the blood of an infected person

  • Unprotected sexual activity with an infected person

  • Needle sharing among intravenous drug users

  • Sharing razors or other personal items with an infected person

  • Being pierced or tattooed with contaminated instruments

  • Blood transfusions (extremely rare in the United States because of improved testing)

  • Childbirth, when the virus is passed from mother to child

Immunization with the hepatitis B vaccine has reduced the number of hepatitis B cases in the United States.

The hepatitis B virus can cause temporary or long-term hepatitis. The initial infection with the virus may not even cause symptoms. When it does cause hepatitis symptoms (acute hepatitis), most people with acute hepatitis B will clear the virus from their systems.

But a minority of people will develop a long-term infection. This is called chronic hepatitis. In chronic hepatitis, the symptoms of hepatitis disappear then come back later. People with chronic hepatitis remain infectious. They can pass on the virus to others.

Some people are not able to rid their body of the infection. But they do not have any symptoms of disease. These people are called carriers. They can pass the infection to others.

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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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