It is named after the West Nile region of Uganda, where it was first isolated in 1937. Outbreaks in humans have occurred in at least 17 countries in Africa and Europe. An outbreak of viral encephalitis in New York City in 1999 that involved 62 people and resulted in 7 deaths was the first recognized introduction of the virus into North America. The virus was probably transported in a person who recently returned from an endemic region, in an imported, infected bird or in an infected mosquito. To estimate the public health impact of the outbreak in New York City, a seroprevalence survey of residents of North Queens, New York, was conducted in the fall of 1999.
Elderly people appear to be more susceptible to severe neurological disease.
3 Last summer New York City implemented a mosquito control and abatement plan that included mosquito surveillance, the elimination of breeding sites and pesticide spraying to kill adult mosquitoes and larvae. In January and February 2000, researchers found low but detectable levels of the virus in 3 of 69 mosquito breeding pools in New York City, suggesting that the virus was able to survive the winter. To date, the virus has not been detected in Canada. Clinical management Symptoms appear 3 to 12 days after a person has been bitten by an infected mosquito. Symptoms range from mild fever and headache, occasionally accompanied by a maculopapular rash that expands from the trunk to the extremities, to severe headache, fever, stiff neck, muscle weakness and disorientation.