Definition of Hepatitis B:

Hepatitis B is inflammation (irritation and swelling) of the liver due to the hepatitis B virus (HBV).

Other types of hepatitis include:

• Hepatitis A
• Hepatitis C
• Hepatitis D

See also:

• Autoimmune hepatitis
• Chronic persistent hepatitis
• Drug-induced hepatitis

Causes, incidence, and risk factors:

The hepatitis B virus spreads through blood, semen, vaginal fluids, and other body fluids. Infection can occur if you have:

• Blood transfusions
• Contact with blood in health care settings
• Had direct contact with the blood of an infected person by touching an open wound or been stuck with a needle
• Had unsafe sex with an infected person
• Received a tattoo or acupuncture with contaminated instruments
• Shared needles during drug use
• Shared personal items (such as toothbrushes, razors, and nail clippers) with an infected person

The hepatitis B virus can be passed to an infant during childbirth if the mother is infected.

The risk of becoming chronically infected depends on your age at the time of infection. Most newborns and about 50% of children infected with hepatitis B develop chronic hepatitis. Only a few adults infected with HBV develop the chronic condition.

Most of the damage from the hepatitis B virus is due to the body's response to the infection. When the body's immune system detects the infection, it sends out special cells to fight it off. However, these disease-fighting cells can lead to liver inflammation.

The liver damage also interferes with the body's ability to get rid of bilirubin, a breakdown product of old red blood cells. This leads to jaundice (yellow discoloration of the eyes and body) and dark urine.