
Hepatitis B is a liver infection caused by the hepatitis B virus (HBV). It is one of several various causes of hepatitis, a condition characteriszed by inflammation and enlargement of the liver. Other causes of hepatitis include, for example, certain drugs, inherited disorders, and autoimmune diseases. HBV is one of five "hepatitis viruses" identified so far. The other four are A, C, D, and E.
The course of HBV infections can vary from a mild form (acute) that lasts only a few weeks to a more serious, chronic, form lasting years. Sometimes chronic HBV leads to serious complications such as cirrhosis or liver cancer.
HBV is spread through contact with blood or other body fluids from an infected person. Exposure can occur, for example, through sharing of needles for IV drug use or through unprotected sex. People who live in or travel to areas of the world where hepatitis B is prevalent are at a greater risk. Mothers can pass the infection to their babies, usually during or after birth. The virus, however, is not spread through food or water, casual contact such as holding hands, or coughing or sneezing.