The Hepadnavirus Family derives its name from its hepatotropic nature and double-stranded DNA genome. While hepatitis B virus (HBV) is the only causative agent for a human disease within the family, a profile on hepatitis D virus or delta agent has also been included due to its specific dependence upon HBV for its propogation.
The human hepatitis B virion consists of an icosahedral nucleocapsid (core) enclosing a circular, double-stranded DNA genome. The hepadnaviral genome is unique in that the plus strand is incomplete, leaving 15-50% of the molecule single-stranded and the minus strand while being complete, possesses a discontinuity at a unique site. The core is surrounded by an envelope containing HBsAg (hepatitis B surface antigens) derived from budding through the lipid bilayer of the endoplasmic reticulum (ER).
Hepatitis B remains a major global concern as some 300 million people are chronic carriers of the virus and of these, a significiant minority suffer severe pathologic consequences including cirrhosis and hepatocellular carcinoma (HCC). Hepatitis B virus is second only to tobacco among the known human carcinogens and studies indicate that HCC may develop with 100 times greater frequency among HBV carriers than controls. Over 1 million of such affected individuals die each year. While a majority of affected adults and older children suffer from acute infection, neonates and infants primarily develop chronic infection. Therefore, patients who develop HCC are individuals who typically became infected with HBV early in life and developed liver cancer 20 to 50 years following primary infection.Update 2000