The hepatitis B virus is globally distributed among humans. The various strains of HBV are quite species specific. Though HBs has been found in other primates, humans remain the principal reservoir. The hepatitis B virus is primarily found in the blood of infected individuals. Virus titres, as high as ten billion virions per millilitre of blood, have been reported in HBe-positive carriers.
Sexual transmission is also possible though inefficient.
There are other potential routes of transmission, but their efficiency is not easily measured. Uninfected individuals living with an HBV carrier are at greater risk of contracting HBV than those not living with a carrier. This is likely due to the fact that HBV can survive even on a dry surface for over a week. However, it should be remembered that for HBV to infect, it still must gain entry into the bloodstream of an uninfected individual. Mosley, J.W. 1975.