Hepatitis B is a serious liver infection caused by the hepatitis B virus (HBV). For some people, the infection becomes chronic, leading to liver failure, liver cancer, or cirrhosis — a condition that causes permanent scarring of the liver.

The hepatitis B virus is transmitted through contact with the blood or body fluids of someone who is infected. Especially at risk for HBV infection are intravenous (IV) drug users who share needles or other drug paraphernalia, people who have unprotected sexual contact with an infected partner, or those who were born in or travel to parts of the world where hepatitis B is widespread. In addition, women with HBV can pass the infection to their babies during childbirth.

Most people infected as adults recover fully from hepatitis B, even if their signs and symptoms are severe. Infants and children are much more likely to develop chronic infections. Although no cure exists for hepatitis B, a vaccine can prevent the disease.