Hepatitis B and C viruses (HBV and HCV) are among the world’s most common infectious pathogens. It is estimated that 500 million people – 1 in 12 of the global population – are chronically infected with one or both of these viruses.1,2 The majority of these people live in the developing world and many of them are unaware that they are infected. Chronically infected patients are at increased risk of developing cirrhosis, hepatic decompensation and hepatocellular carcinoma (HCC), which together account for more than 1 million deaths annually.3 Hepatocellular carcinoma is one of the most common cancers worldwide, and HBV is thought to be responsible for about 75% of all cases.4 There is a strong correlation between the prevalence of HBV carriers and the incidence of HCC (Figure 1-1).5
Figure 1-1. Geographic distribution of HBV prevalence and incidence of HCC5
The prevalence of chronic Hepatitis B (CHB), varies greatly among different areas of the world (Figure 1-1).5 Areas of high endemic prevalence (≥8%) include South East Asia, Africa, the Pacific Islands and the Arctic; in these regions, the major means of transmission is by perinatal infection at birth or horizontally, from individual to individual, in early childhood.6 The predominant routes of transmission in these areas of high endemicity have important consequences, as the younger the age of HBV acquisition, the higher the probability of chronicity and associated problems.6 Outside of highly endemic areas, other regions with high rates of HBV infection include Southern, Eastern and Central Europe, the Amazon Basin, the Middle East and the Indian subcontinent. Areas of low prevalence (<2%) include Western Europe, North America and Australasia; in these regions, infection often occurs in adulthood, with the main mode of transmission being sexual contact and injecting drug users.7,8
In recent years, the geographic epidemiology of HBV infection has changed due to increased migration of people from highly endemic areas.9,10 Hence, even countries with low endemicity are experiencing the burden of HBV.
Due to an extensive vaccination policy in the developed world, the incidence of HBV infection is decreasing, together with rates of HCC in children.11 However, the burden on healthcare systems from the existing pool of chronically infected people is still increasing, since the long-term complications of CHB only become apparent after about 20–30 years, and vaccination has only been in place since 1982.
References:
1. World Health Organization. World Health Organization Hepatitis B Fact Sheet. 1998.
2. World Hepatitis Alliance. www.aminumber12.org
3. Lai CL, Ratziu V, Yuen MF, Poynard T. Viral hepatitis B. Lancet 2003;362:2089–94.
4. Beasley RP. Hepatitis B virus. The major etiology of hepatocellular carcinoma. Cancer 1988;61(10):1942–56.
5. Hepatitis B vaccines. 2007. (Accessed 2003 at www.who.int.)
6. Maddrey WC. Hepatitis B: an important public health issue. J Med Virol 2000;61(3):362–6.
7. Lok AS, Heathcote EJ, Hoofnagle JH. Management of hepatitis B: 2000 – summary of a workshop. Gastroenterology 2001;120(7):1828–53.
8. Gust ID. Epidemiology of hepatitis B infection in the Western Pacific and South East Asia. Gut 1996;38(Suppl 2):S18–23.
9. Chu CJ, Keeffe EB, Han SH, et al. Hepatitis B virus genotypes in the United States: results of a nationwide study. Gastroenterology 2003;125(2):444–51.
10. Kim WR, Benson JT, Therneau TM, Torgerson HA, Yawn BP, Melton LJ, 3rd. Changing epidemiology of hepatitis B in a U.S. community. Hepatology 2004;39(3):811–6.
11. Chang MH, Chen CJ, Lai MS, et al. Universal hepatitis B vaccination in Taiwan and the incidence of hepatocellular carcinoma in children. Taiwan Childhood Hepatoma Study Group. N Engl J Med 1997;336(26):1855–9.
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