Different types of data are available to describe the epidemiology of HBV infection. Most industrialized countries have systems in place to register/notify cases of hepatitis B (acute hepatitis B disease:symptomatic/clinical cases only; all cases: symptomatic plus asymptomatic cases) to a centralised health authority. These surveillance systems allow the estimatation of the incidence of hepatitis B, which provides the best estimate for the risk for this condition.