The Basics of the West Nile Virus

According to the CDC:

West Nile fever is an illness caused by the West Nile Virus (WNV), believed to be carried into the U. S. by a bird, person, or mosquito. It begins with flu symptoms, and may progress to coma and death in 3-15% of infected people. The elderly are more apt to die. Symptoms may include a rash and weakened leg muscles. One in 50 infected people will develop serious symptoms of encephalitisãswelling of the brain.

Birds are the host for this virus (where it lives) and mosquitoes are the vector (mode of transmission). If an infected mosquito takes a "blood meal" from (i.e., bites) a human, the mosquito can transmit the West Nile Virus to that person. In 1999, for the first time, the West Nile Virus was found in the U. S., causing an outbreak of West Nile encephalitis in New York City, resulting in 62 severe cases and 7 deaths. While additional cases occurred in 2000 and 2001, there was a dramatic increase in West Nile virus cases and in the area affected by the virus in 2002. There were more than 4000 human cases reported, and 284 deaths, and the virus spread as far as the West Coast.

Who's at Risk?

Anyone can become ill from a West Nile Virus infection, however people over age 50 are most at risk of severe diseases coma and death.