West Nile Virus

West Nile virus Encephalitis is a mosquito-borne viral disease, which can cause an inflammation of the brain and can be a serious, even fatal, illness.

West Nile virus is common in Africa, West Asia, the Middle East and Europe and experts believe it is now established as a seasonal epidemic in North America.

West Nile virus appears in summer in North America and outbreaks often carry on into autumn - in 1999 the virus was confirmed in the New York metropolitan area during the summer and fall, it survived the winter and has since then been present in humans, horses, certain birds, and mosquitoes.

West Nile virus is most often spread by the bite of an infected mosquito - mosquitoes become infected when they feed on infected birds - the infected mosquitoes can then spread the virus to humans and other animals when they bite.

West Nile virus is not spread through touching or through casual contact such as touching or kissing a person with the virus, but in a few cases it has been spread through blood transfusions, organ transplants, breastfeeding and even during pregnancy from mother to baby.

Since 1999, West Nile virus has spread rapidly across the United States following the pattern of migratory birds and has emerged in all states except Maine and Washington and into parts of Canada, Mexico, Central America, and South America.

West Nile virus is a potentially serious illness for which there is no human vaccine and it is important that the public has information that can help them recognize and prevent West Nile virus.

This is a transmission electron micrograph (TEM) of the West Nile virus (WNV). See PHIL 2290 for a black and white version of this image. Photo Credit: Cynthia Goldsmith

Further Reading

• All West Nile Virus Content
• West Nile Virus Symptoms, Risk, Treatment
• West Nile Virus Prevention
• West Nile Virus in Pets and Other Animals
• Testing for West Nile Virus