4.4.1  Definition, cause and occurrence of hepatitis B

Hepatitis is a term referring to a serious inflammation of the liver. Several viruses can cause hepatitis, but the hepatitis B virus (or HBV) is the most important one. Hepatitis B disease is a major global health problem and the most serious type of viral hepatitis. The WHO estimates that an estimated two billion people have been infected with HBV worldwide, and more than 350 million have chronic (long-term) liver infections. About 600,000 people die every year as a result either of acute liver infection, or of chronic liver damage or liver cancer, which develops slowly over decades and eventually leads to their death.

4.4.2  Mode of transmission and clinical manifestation of HBV