Hepatitis B Virus
Hepatitis B virus, HBV, is a part of the Hepadnaviridae family of viruses. HBV can lead to cirrhosis and hepatocellular carcinoma and has been linked to pancreatic cancer.
It is classified as a species of the Orthohepadnavirus. Similar viruses have been found worldwide in great apes and monkeys. There a few different genotypes and they all differ by at least 8% of the sequence and have distinct geographical distributions and this has been associated with anthropological history. Type A is in Europe, Africa, and South-east Asia. B & C are in Asia while D is common in the Mediterranean, Middle East, and India. E is localized in sub-Saharan Africa. F is in central and south America while Type G is in France and Germany. A, D, and F are predominant in Brazil and all of them occur in the United States. There are 24 subtypes within the main genotypes.
Hepatitis B is complex and is one of a few known non-retroviral viruses which use reverse transcription as a part of its replication process. After binding to a receptor on the surface the virus enters the cell through endocytosis. After fusing with the cell membrane the virus releases mRNA and core proteins into the cytoplasm.