The hepatitis B virus is classified by the World Health Organisation (WHO) as the world’s second greatest carcinogen after tobacco.
Type B hepatitis is caused by the hepatitis B virus (HBV), a small enveloped DNA virus that infects the liver causing hepatocellular necrosis and inflammation. HBV can cause either an acute illness or chronic, persistent infection. Acute or chronic infection can lead to severe liver damage and is therefore potentially fatal.
After the identification in 1965 of the hepatitis B surface antigen, called HBsAg, hepatitis B was clearly linked to the development of cirrhosis and primary liver cancer. The virus and subviral particles were identified in serum and the genome of the virus was isolated and characterised as a small circular molecule of DNA.
Structure of the hepatitis B virus
(Acknowledgement: Baruch S. Blumberg)
The identification of HBV led to the development of vaccines using HBsAg particles isolated from the serum of chronic carriers and later, after the genome of the HBV had been cloned, recombinant DNA vaccines.
HBV has been classified into eight genotypes, each with a distinct geographical and ethnic distribution:
Genotypes A and D - Africa, Europe and India
Genotypes B and C - Asia
Genotype E - West Africa
Genotype F - Central and South America
Genotype G - France, Germany and the USA
Genotype H - Central America
Hepatitis B presents clinical staff with many difficult challenges. Disease management is still developing, influenced by the introduction of new drugs and the evolution of new data. Treatment is complicated, may be costly and time consuming. While there is an effective vaccination for HBV, it is not universally available. Dealing with patient uncertainties about therapy and the social and occupational implications arising from this may present further problems.
This section reviews current understanding about hepatitis B and provides a framework for optimal management of the disease by health professionals.