about the number and geographic distribution of HBV genotypes and naturally occurring HBV mutants are gained. Eight HBV genotypes, A to H, have been identified in human and three closely related genotypes in apes are found, like gibbon, orangutan, chimpanzee; and he eight HBV genotypes have further diverged into at least 24 subgenotypes. With different analysis, including analysis of recombinants, the new Genotype J was provisionally assigned to be a genetic variant of HBV which is divergent from known human and ape genotypes, it was isolated from a Japanese patient. Avihepadnavirus Viruses in this genus exclusively infect birds; duck hepatitis B virus (DHBV) and heron hepatitis B virus (HHBV) are the prototypes. Avihepadnaviruses have been detected in various duck species. As the same with the orthohepadnaviruses, avihepadnaviruses have a rather narrow host range, but its common host are ducks and geese, other possible hosts are herons, stocks and crane. Differences between orthohepadnaviruses and avihepadnaviruses Low nucleotide sequence identity Differences in genome size, with genomes of orthohepadnaviruses generally larger than that of avihepadnaviruses Larger core proteins and no M surface for avihepadnaviurses; for orthohepadnaviruses, virions and filaments are enriched in L proteins and empty spheres consist predominantly of S proteins, while for duck hepatitis B virus, L and S proteins are distributed evenly between particle types Different host range restrictions (exclusively mammals for orthohepadnaviruses and exclusively birds for avihepadnaviruses) Different predominant transmission strategies (horizontal transmission for orthohepadnaviruses and vertical transmission for avihepadnaviruses) Transmission Orthohepadnaviruses Within humans Horizontal Direct transmission person-to-person From healthcare workers Sexual contact Parenteral exposure Indirectly Unsafe medical practices Transfusions and haemodialysis Vertical Perinatal period Mother-to-offspring Until 2000, there were more than 5.2 million cases of acute hepatitis B infection, and chronically infects approximately 5% of the human population. HBV is the most common one among those hepatitis viruses. It can cause chronic infection of liver in humans, which has become a global public health problem, since chronic hepatitis can cause cirrhosis or death from liver failure within certain times. And it is the major cause of HCC, contributing about 60-80% of the HCC cases around the world. HBV is transmitted by parenteral contact with body fluids, such as blood and lymph; perinatal exposure of infants to carrier mothers. It is thought that mother-to-child perinatal transmission and the establishment of a lifelong highly infectious carrier state are responsible for the observed high rates of endemicity in high-prevalence regions such