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Several viruses are capable of causing hepatic inflammation. These include
the Epstein-Barr virus, cytomegalovirus, herpes simplex virus, mumps,
rubella, rubeola and varicella-zoster viruses, yellow fever virus, Coxsackie
viruses, and adenoviruses. In most cases, infection or inflammation of the
liver is part of a systemic infection with the above agents. In addition, there
are a number of viruses that are primarily hepatotropic and are given alphabetical
designations: hepatitis A–E. Several other viruses that were initially
thought to cause posttransfusion hepatitis, including hepatitis G virus or
GBV-C and SEN viruses, are not currently believed to be human pathogens.
Of the truly hepatotropic viruses, hepatitis A and hepatitis E generally produce
self-limited disease, although fulminant hepatic failure has been
reported in up to 1%–2% of infected individuals. Hepatitis D virus (or
the delta agent) can produce coinfections in patients who are infected with
hepatitis B, but it appears to be incapable of causing serious disease in the
absence of hepatitis B virus. Hepatitis B and C viruses are arguably the most
important viruses of this group. In addition to acute infections, exposure to
these viruses frequently results in a chronic persistent infection that may
remain asymptomatic or lead to cirrhosis, liver failure, and hepatocellular
carcinoma. Chronic infections with hepatitis C virus are currently responsible
for an increasing percentage of liver transplantations performed in the
United States and elsewhere. Because of the large number of patients worldwide
who suffer from chronic infections with these two agents, they are
arguably the most important viral cause of carcinoma in the world. In recent
years, we have learned a great deal about the biology of hepatitis B and C
viruses and have gained increasing knowledge of the pathophysiology of the
disease they cause in the liver. Concomitant with our understanding of these
processes has been the development of a variety of therapeutic modalities,
ranging from relatively specific, classic antiviral agents (including lamivudine,
adefovir, tenofovir, ribavirin, and a number of new investigational
agents) to drugs such as interferon-a, which also have immunomodulatory
effects. Vaccine strategies likewise play an important role in preventing
hepatitis B. |
