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Numerous pathogens can directly or indirectly cause hepatitis. However, primary viral infection of the liver is most commonly caused by several specific hepatotropic viruses. Several such viruses have been identified, in particular A, B, C, D, E, and G (Table 40–1). The characteristics, epidemiology, clinical features, and management of these viruses differ significantly. The discussion here will focus largely on viral hepatitis caused by hepatitis A, B, and C.
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Hepatitis A virus (HAV) is a common infection in the United States and worldwide. The incidence in the United States has declined significantly with the introduction of the vaccination.1,2 The incidence of reported acute HAV has declined to 1.5 cases per 100,000 people. Some of this decline may also be attributable to an improvement in hygiene and sanitation practices. HAV is spread by the fecal–oral route, from person to person, and is highly contagious. A typical setting for an outbreak of HAV infection is a childcare center, especially one that includes children who are not yet toilet trained. International travelers to developing countries are also at particular risk of contracting HAV. Parenteral transmission of HAV, although uncommon, has been reported.3
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Hepatitis B virus (HBV) remains a global health problem, despite the availability of an effective vaccine. Approximately 1 million individuals die from HBV-related liver disease each year.4 The prevalence of HBV carriers varies from 0.1% to 2% in Western countries to 10–20% in southeast Asia and sub-Saharan Africa.4–7 With the implementation of universal vaccination in 1991 within the United States, acute HBV incidence has declined significantly, to the lowest rate ever recorded: 1.8 cases per 100,000 people in 2005.2 Declines occurred among all age groups but were greatest among children aged younger than 15 years. In Western countries, the majority of children with newly acquired HBV are immigrants, the children of immigrants, and adoptees.
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