Orthohepadnaviruses Within humans *Horizontal *Direct<unk>  *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<unk>  and the establishment of a lifelong highly infectious carrier state are responsible for the observed high rates of endemicity in high-prevalence regions such as South and East Asia and sub-Saharan Africa. In some cases breast milk of HBsAg positive mothers has been found to be positive for the virus, but there have not been any reports of HBV<unk>  through breast-feeding, even before the availability of hepatitis B vaccine for infants. *Horizontal<unk> : through directly contacts with infected body fluids, like blood and lymph, in ways like sexual contacts, from health-care workers, or parenteral exposure; indirectly through transfusions and haemodialysis, and contaminated medical practices. *Vertical<unk> : through perinatal periods, mother to child. Cross-species<unk>  Cross-species<unk>  has not been proven yet, but if this occurs, the chance to eradicate HBV infection by immunization will be diminished due to the difficulty in controlling of natural virus reservoir. And increasing human encroachment on rainforest habitat and fragmentation of declining populations increases the interactions and consequently the risks of disease<unk>  between wild primates and human populations.<unk>  of mammalian<unk> trains between cross-species primate hosts has been found in many cases, recombination of<unk> trains from cross-species primate hosts, further demonstrates that primate associated HBV strains can indeed share hosts in nature, and cross-species<unk>  of primate-associated HBV strains provides the probability of interspecies recombination. Within non-human mammals * Gibbon HBV: Between gibbon and chimpanzee: the inoculation of GiHBV to a chimpanzee resulted in the acute hepatitis infection, and the virus isolated from the infected chimpanzee was GiHBV too. * Woolly monkey HBV: Since black-handed spider monkey belongs to the same family and subfamily as the woolly monkey, it was chosen as a suitable small primate model to study WMHBV. The results showed that the black-handed spider monkey was susceptible to WMHBV, but developed only a subclinical infection. The susceptibility of chimpanzees to WMBHV was only limited. * WHV: has only been detected in eastern woodchucks (Marmota monax), and does not infect related alpine marmosets. It infects woodchucks, but not other rodents like ground squirrels. But HDV with a WHV envelope (wHDV) has been shown to infect chimpanzees, and primary human hepatocytes. Vice versa a human enveloped hHDC could enter and (transiently) infect woodchuck hepatocytes in vivo without the need for a helper virus, but an infection of woodchucks or primary woodchuck hepatocytes with HBV has not been described. * GSHV: infects woodchucks and ground squirrels, specifically some species of squirrel (Spermophilus beecheyi and Spermophilus richardsonii) and the phylogenetically closely related chipmunks. GSHV runs a milder course when inoculated into woodchucks with the delayed onset of HCC. Between humans and non-human mammals Since the similarity between human and apes, and common ancestors human and apes shared long time ago, there are possibilities to happen<unk>  of HBVs among them. The prevalence of HBV infection in the natural primate habitat is unknown. Most data resulted from the studies performed on samples obtained from captive animals, wild-born or captive-born. Human HBV infects only humans and closely related primates, such as chimpanzee, chacma baboon, and to some extent, tree shrew, but does not infect woolly monkeys. HBV isolates have been shown to infect gibbon apes and chimpanzees, but not convincing evidence of an infection of macaques or other members of the Cercopithecidea family. Macaca sylvanus is able to replicate HBV in vivo replication in primary macaque hepatocytes. However, susceptibility of these animals has not been shown. * Gibbons: studies show that the vertical<unk>  is essential in the<unk>  of HBV in the non-human primates. But, there is also a possibility of horizontal<unk>  confirmed by HBV DNA detection in gibbon saliva. If the gibbons were housed in the same habitat, they would likely transmit HBV to the other gibbons through sexual contact or horizontal<unk>  of family members. * Chimpanzees: viral hepatitis had been known to occur in captive chimpanzees even prior to the discovery of HBV. Many studies used the chimpanzee models which have been limited now, showed that shortly after the first cloning of the HBV genome, the cloned DNA was infectious in chimpanzees, mostly developed hepatic pathology similar to the acute HBV infection in human, but they did not develop a chronic liver disease. * Tupaias: they are susceptible to the human HBV. However, the experimental infection is not highly efficient and causes only a mild, transient infection with low viral titers. Primary hepatocytes isolated from the liver of Tupaias are well susceptible to HBV infection. * Mice: Several researchers developed transgenic mice in order to study the expression of coding regions for the surface antigens, products of preS, S, and X gene of HBVs. The transgenic mice were not susceptible to HBV, but mice with severe combined immunodeficiency (SCID) can develop chronic liver disease. In addition, they permitted HBV to replicate in human hepatocytes that were able to proliferate in these mice. In general, these results imply that nonhuman primate HBV variants may be transmittable to humans. At least they infect representatives of the families Pongidae and Hylobatidae. However, at present it remains to be elucidated if nonhuman primate HBV variants are transmittable to humans and whether they cause disease in humans. And till now, no report of HBV<unk>  from captive animals to humans currently exists. However the potential for zoonotic disease<unk>  exists where blood or body fluid exposure is common. Such scenarios could include chronically infected animals kept as family pets, close contact with caretakers, in situations in which chimpanzees are slaughtered and used as bushmeat. Avihepadnaviruses Within birds Many cases about avihepadnaviruses<unk>  between or within species have been studied. * DHBV: infects only certain duck and goose species, but does not even infect Muscovy ducks or chickens, or infects them inefficiently. * Heron HBV: does not infect ducks and only infects primary duck hepatocytes very inefficiently. Studies on different heron species which are geographically isolated populations suggest that lateral<unk> , virus adaptation and environmental factors all play a role in HHBV spreading and evolution, but it is not clear whether HHBV infection occurs at all in free-living herons, due to the possibility of cross-species virus<unk> . * Crane HBV: cranes are phylogenetically very distant from ducks and are more closely to herons and stocks, but CHBV infects primary duck hepatocytes with efficiency similar to DHBV. Between humans and birds There is no evidence for<unk>  of avian hepadnavirus between avian and human, but recombination of avihepadnavirus strains between cross-species avian hosts can offer potentials for the<unk>  between human and bird, considering that many birds are one of the main sources of food for human. Factors affecting<unk>  ;Species specificity The special replication strategy gives this genus a special character, but also the high replication capacity and high error rate of the viral reverse transcriptase, thus HBVs from this genus have the ability to adapt to the host's environment, and varies from different<unk> , thus exhibiting species specificities. ;Proteins Pre S1 regions of the L protein, exhibiting different host specificity, if proteolytically being removed from HBV particles results in a loss of infectivity. The S protein therefore is needed, but not sufficient for HBV entry. In contrast to the M protein, the L protein is essential for the viral infectivity. These special proteins plays different role in different viruses, thus determining the different host ranges, if this were strictly true, we would expect that divergence in pre-S would affect cross-species infection, which then can contribute the different<unk>  of different<unk> . *Replacing the special region of the envelope protein of one hepadnavirus with another<unk> . *HHBV by DHBV:infect ducks and derived primary hepatocytes *WMHBV by HBV:infect human hepatocytes *Subviral sphere particles: They are assumed to have the ability of absorbing virus-neutralizing antibodies to facilitate the virus spread and maintenance in the host. Potentials ;Co-infection A lot of studies have well characterized the horizontal<unk>  of HBV through parenteral routes and co-infections with different genotypes of HBV have also been reported, including genotypes A and D, genotypes A and G, and genotypes B and C. In Asia, genotypes B and C account for almost all HBV infections. Infection with genotype C may induce more severe liver diseases than infection with genotype
Transmission of hepadnaviruses
Waterborne diseases
Antibiotic use in livestock
Transmission of COVID-19
Prevention of viral hemorrhagic fever
Pesticide toxicity to bees
Blood-borne disease
Intentional contagion of infection