Studying the Treatment of Chronic Hepatitis B Viral Infection in Special Populations

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Abstract

There are estimated to be more than 400 million people chronically infected with the hepatitis B virus (HBV) worldwide (Fig. 1) (1). At least 20–30% of those chronically infected will die of complications of chronic liver disease including cirrhosis and liver cancer (2,3). The World Health Organization (WHO) places HBV in the top 10 causes of death worldwide (4). The estimated viral burden in the United States is 1.5 million people, with disease concentrated in ethnic subgroups and populations with high-risk behavior, and health care costs to the North American economy that exceed $350 million per year. Although the United States is considered an area of low-prevalence hepatitis B infection, the incidence of new cases, the prevalence of carriers, and the burden of acute and chronic disease maintain hepatitis B high among the important communicable diseases. It is estimated that 300,000 new cases of hepatitis B infection occurred each year in the United States in the 1970s and 1980s. Currently about 125,000 new cases occur each year in North America. These acute infections have led to at least 27,000–42,000 chronic carriers, 17,000 hospitalizations, 300 cases of fulminant liver failure, and ultimately 4000–5500 deaths per year in the United States from cirrhosis and primary liver cancer as well as the morbidity and cost of liver transplantation in approx 350 patients per year (511). The age-specific incidence of acute HBV infection is shown in Fig. 2. The risk of developing chronic HBV infection after acute exposure ranges from 1% to 5% for adults and 90% for infants born to infected mothers (Fig. 3). Once chronic infection has occurred, a heterogeneous group of patients or clinical profiles is evident based on a combination of viral replication, fibrosis progression, host immune response, and presence or evolution of viral mutants. Fig. 1.

The 350 million chronic carriers of HBV worldwide account for more than 5% of the world’s population. Although widely distributed, the prevalence of HBV varies from a highly endemic disease (>8%) in China, Southeast Asia, and Africa to a disease of low endemicity (>2%) in North America, western Europe, and Australia. Areas with intermediate levels of prevalence (2–7%) are also noted. In most developed countries, the prevalence of chronic HBV infection is >2%. Within these areas reside ethnic groups with HBV infection rates that are significantly higher than those of the general population, for example, Eskimo populations in Alaska and Canada and the Maoris in New Zealand. (WHO Statistics [166].)
Fig. 2.
Age-specific incidence of acute hepatitis B in the United States from 1982 to 1998. The median age increased from 27 to 32 yr, with 61% males. Age groups: gray line, 10–19 yr; dashed line, 20–29 yrs; dotted line, 30–39 yr; solid line, 40’49 yr. (Centers for Disease Control, Sentinel Counties Study.)
Fig. 3.
Carrier state and recovery.