West Nile encephalitis is an infection of the brain caused by the West Nile
virus, a flavivirus found in Africa, West Asia and the Middle East, with outbreaks
having been reported in Europe. It is closely related to the St. Louis encephalitis
virus found in the United States. Centers for Disease Control scientists believe
the virus has probably been in the eastern United States since the early summer
of 1999, possibly longer. The most serious manifestation of West Nile virus
infection is fatal encephalitis in humans and horses, as well as mortality in
certain domestic and wild birds.
In humans, less than 1 percent of those infected with West Nile virus will
develop serious illness, however, among those with severe illness, the fatality
rate ranges from 3 percent to 15 percent and will be highest among the elderly.
West Nile virus has been identified in more than 100 species of birds in the United States, and most of these birds were identified through reports from the public. The Texas Department of Health requests dead bluejays or crows be reported to its hotline, (800) 252-8239, or nearest city or county health unit.
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