West Nile Virus and West Nile Encephalitis (WNE)
West Nile Virus Facts
West Nile Virus Overview
West Nile virus is a Flaviviridae virus transmitted to humans by mosquito bites. Virus symptoms range from none to severe: encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord). The disease the virus causes is termed West Nile encephalitis (WNE). WNE currently is endemic in Asia, Africa, and the Middle East. Since 1999, the disease has been detected in many states (see map below) in the U.S. The disease is considered to be endemic now in the U.S.; in 2013, 39,567 individuals had been diagnosed with the disease. From 2013-2015, about 2,000 per year are detected with new West Nile infections in 47 states in the U.S.
West Nile virus was discovered in 1937 in the West Nile district of Uganda. Although wild birds are the preferred hosts for the virus and are likely the hosts that spread the disease from country to country, West Nile virus can infect other mammals such as horses and dogs, for example. The virus is transferred from animal or birds to humans by mosquitoes. Since the virus was first detected in the United States in 1999, every year since then there has been an outbreak in the U.S. of West Nile virus (for example, outbreaks have occurred in California, Arizona, Illinois, Massachusetts, Oregon, Pennsylvania, Wisconsin, and Texas); the virus has been detected in 47 U.S. states and in Canada.
Medically Reviewed by a Doctor on 4/9/2015
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West Nile encephalitis (WNE) is distinguished from other arthropod-borne causes of viral encephalitis (eg, western equine encephalitis, eastern equine encephalitis [EEE], Japanese encephalitis, Venezuelan encephalitis) based on its geographic distribution, clinical features, and laboratory findings.