of liver cirrhosis are caused by chronic HBV or HCV infection (Perz et al., 2006). Chronic liver disease due to coinfection with HBV or HCV has become a major cause of death in persons infected with HIV (Sulkowski, 2008), and coinfection presents additional treatment challenges (Kumar et al., 2008). It is estimated that HBV and HCV infections cause nearly a million deaths each year (Perz et al., 2006).

Chronic viral hepatitis is a silent killer. Without testing for infection, many chronically infected persons are not aware that they have been infected until symptoms of advanced liver disease appear. Advanced liver cancer has a 5-year survival rate of below 5% (American Cancer Society, 2009). Although much progress has been made in reducing the morbidity and mortality through effective treatment of chronic viral hepatitis, there is no global program to provide chronically infected persons with access to affordable treatment.

HBV is 50–100 times more infectious than HIV (WHO, 2009). Acute HBV infection in adults, although often asymptomatic, can cause severe illness and is associated with a 0.5–1% risk of death from liver failure (CDC, 2007). Chronic HBV infection, which occurs when the acute infection is not cleared by the immune system, is associated with a 15–25% risk of premature death from liver cancer or end-stage liver disease (Beasley and Hwang, 1991; WHO, 2009). The World Health Organization (WHO) estimates that up to 2 billion people worldwide have been infected with HBV; about 350 million people live with chronic HBV infection, and about 600,000 people die from HBV-related liver disease or HCC each year (WHO, 2009).

The major transmission routes and prevalence of chronic HBV infection vary by age and geography. Primary HBV infection acquired at an early age (through vertical transmission from an infected mother to her newborn or horizontal transmission during early childhood) is associated with the highest risk of chronic infection and is common in people born in or residing in the highly endemic countries of the western Pacific region, Asia, and sub-Saharan Africa (Shepard et al., 2006). In countries with a low prevalence of HBV carriers, primary infection usually occurs during adolescence or young adulthood as a result of unsafe injections and unprotected sexual activity. An estimated 21 million new HBV infections each year are due to unsafe injections in health-care settings (Hauri et al., 2004). Hepatitis B is also a major basis for social injustice in some endemic countries. For example, myths and misinformation about modes of HBV transmission have resulted in widespread discrimination against chronically infected persons in some endemic countries, such as China, the country with the world’s largest population of chronically infected people, who are not allowed to work in the food industry, are often required to undergo routine pre-employment HBV testing, and can be expelled from school or work because of a positive test (The Economist, 2006).



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