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Jaundice is the disease that your friends diagnose.
—Sir William Osler
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The causes of hepatitis (inflammation of the liver) are varied and include viruses, bacteria, and protozoa, as well as drugs and toxins (eg, isoniazid, carbon tetrachloride, and ethanol). The clinical symptoms and course of acute viral hepatitis can be similar, regardless of etiology, and determination of a specific cause depends primarily on the use of laboratory tests. Hepatitis may be caused by at least five viruses belonging to different virus families, whose major characteristics are summarized in Table 13–1. Non-A, non-B hepatitis is a term previously used to identify cases of hepatitis not due to hepatitis A virus (HAV) or hepatitis B virus (HBV). With the discovery of hepatitis C and E viruses (HCV and HEV, respectively), virtually all the viral etiologies of non-A, non-B hepatitis can be specifically identified. One additional hepatitis virus, hepatitis G virus (HGV), has been identified that is not associated with any clinical disease so far but found in some blood donors as well as some patients who are either infected with HCV or human immunodeficiency virus (HIV). Other viruses, such as Epstein-Barr virus and cytomegalovirus, can cause inflammation of the liver, but hepatitis is not the primary disease caused by them. Yellow fever is also associated with hepatitis, but is described in Chapter 16.
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Hepatitis A virus (HAV) belongs to the Picornaviridae (picornaviruses) family and Hepatovirus genus. It is an unenveloped (naked capsid), single-stranded, positive-sense RNA virus with a cubic (icosahedral) symmetry and a diameter of 27 nm (Figure 13–1). The genome of HAV is a 7.4 kb positive-sense, single-stranded RNA bound to a protein called VPg, and each capsid unit comprises four proteins, VP1, -2, -3, and -4, which cover ...