Hepatitis B virus

Hepatitis B virus
TEM micrograph showing hepatitis B viruses
Virus classification
Group:	Group VII (dsDNA-RT)
Order:	Unassigned
Family:	Hepadnaviridae
Genus:	Orthohepadnavirus
Species:	Hepatitis B virus

Hepatitis B virus, abbreviated HBV, is a species of the genus Orthohepadnavirus, which is likewise a part of the Hepadnaviridae family of viruses. This virus causes the disease hepatitis B.

In addition to causing hepatitis, infection with HBV can lead to cirrhosis and .

It has also been suggested that it may increase the risk of pancreatic cancer.

The hepatitis B virus is classified as the type species of the Orthohepadnavirus, which contains three other species: the Ground squirrel hepatitis virus, Woodchuck hepatitis virus, and the Woolly monkey hepatitis B virus. The genus is classified as part of the Hepadnaviridae family, which contains two other genera, the Avihepadnavirus and a second which has yet to be assigned. This family of viruses have not been assigned to a viral order. Viruses similar to hepatitis B have been found in all apes (orangutan, gibbons, gorillas and chimpanzees), in Old World monkeys, and in a New World woolly monkeys suggesting an ancient origin for this virus in primates.

The virus is divided into four major serotypes (adr, adw, ayr, ayw) based on antigenic epitopes present on its envelope proteins. These serotypes are based on a common determinant (a) and two mutually exclusive determinant pairs (d/y and w/r). The viral strains have also been divided into ten genotypes (A–J) and forty subgenotypes according to overall nucleotide sequence variation of the genome. The genotypes have a distinct geographical distribution and are used in tracing the evolution and transmission of the virus. Differences between genotypes affect the disease severity, course and likelihood of complications, and response to treatment and possibly vaccination. The serotypes and genotypes do not necessarily correspond.

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