Encephalitis is rare in the United
States; about 20,000 cases are reported every year.1
Outbreaks can occur, causing the number of cases
to be much higher, but these are uncommon in the U.S. But in 2002, an
outbreak of mosquito-borne West Nile virus in the U.S. caused numerous
infections and deaths. Still, far more people who have
West Nile virus develop mild or no symptoms rather
The number of cases caused by mosquito-borne
viruses varies by location throughout the world. In the U.S.,
mosquito-borne encephalitis (such as St. Louis encephalitis, La Crosse
encephalitis, and West Nile encephalitis) is rare. Tick-borne viral
encephalitis is even rarer.
Infection with the
rabies virus can cause encephalitis and is almost
always fatal if it is not treated before symptoms develop.
impaired immune systems, especially those with AIDS
(acquired immunodeficiency syndrome), are at increased risk of developing
toxoplasmosis, and other infections.
CitationsRoos KL, Tyler KL (2008). Meningitis, encephalitis,
brain abscess, and empyema. In AS Fauci et al., eds, Harrison's Principles of Internal Medicine, 17th ed., vol. 2, pp. 2621–2641. New
October 26, 2011
E. Gregory Thompson, MD - Internal Medicine & W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
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