The prevalence of hepatitis B is highest in the Western Pacific Region and African Region, where 6.2% and 6.1% respectively of the adult population is infected. In Eastern Mediterranean Region, South-East Asia Region and European Region, an estimated 3.3%, 2.0% and 1.6%% of the general population is infected, respectively. 0.7% of the population of the Americas is infected.
In highly endemic areas, hepatitis B is most commonly spread from mother to child at birth (perinatal transmission), or through horizontal transmission (exposure to infected blood). Hepatitis B is also spread by percutaneous or mucosal exposure to infected blood and various body fluids. Transmission of the virus may also occur through the reuse of needles and syringes either in health-care settings or among persons who inject drugs. In addition, infection can occur during medical, surgical and dental procedures, through tattooing, or through the use of razors and similar objects that are contaminated with infected blood.