EPIDEMIOLOGY AND NATURAL HISTORY OF HEPATITIS B

EPIDEMIOLOGY Approximately one third of the world’s population has serological evidence of past or present infection with hepatitis B virus (HBV) and about 400 million people, particularly in developing countries, are chronically infected. It is estimated that worldwide over 200000 and 300000 chronic HBV carriers die each year from cirrhosis and hepatocellular carcinoma (HCC), respectively (1,2). Three different patterns of hepatitis B endemicity (high, intermediate and low) with well-defined geographic distribution have been recognized (3). The prevalence of HBV infection is especially high in South-East Asia, Sub-Saharan Africa and the Western Pacific where more than 8 % of the population are chronic hepatitis B surface antigen (HBsAg) carriers. In areas with this pattern perinatal transmission or transmission during early childhood are responsible for the high rate of chronic HBV infection. In most developed parts of the world the prevalence of chronic HBV infection is less than 1%. Within these areas of low hepatitis B endemicity most infections occur among high risk adult populations that includ