West Nile virus is a member of the family of viruses called Flaviviridae. The virus is primarily an infection that kills birds, but it can be transmitted to mammals, including humans, by the bite of a mosquito. Native to the Middle East, Africa, and western Asia, West Nile spread to Europe and North America in the late 1990s.
Only about 20 percent of infected people suffer any ill effects at all. Ordinary West Nile fever produces aches and pains, nausea and vomiting, and other flu-like symptoms that typically disappear after only a few days. However, about 1 person in 150 will become seriously ill and may develop a brain infection called encephalitis. The virus can also affect the tissues around the brain, where it causes a form of meningitis,
Only about 20 percent of infected people suffer any ill effects at all. Ordinary West Nile fever produces aches and pains, nausea and vomiting, and other flu-like symptoms that typically disappear after only a few days. However, about 1 person in 150 will become seriously ill and may develop a brain infection called encephalitis. The virus can also affect the tissues around the brain, where it causes a form of meningitis,