An Introduction to the West Nile Virus
West Nile virus disease (simply known as West Nile virus or WNV) is a potentially serious illness caused by the West Nile virus. Experts believe that West Nile virus is established as a seasonal epidemic in North America; it flares up in the summer and continues into the fall.
Understanding the West Nile Virus
The West Nile virus is a flavivirus (transmitted by ticks and
mosquitoes) commonly found in Africa, West Asia, and the Middle East. It is closely related to the
St. Louis encephalitis virus, which is also found in the United States. The West Nile virus can infect humans, birds, mosquitoes, horses, and some other mammals.
The length of time that the West Nile virus has been in the United States is unknown, but scientists believe the virus has probably been in the eastern United States since the early summer of 1999, or possibly longer.
Causes of West Nile Virus
Most often, West Nile virus is spread by the bite of an infected mosquito. In rare cases, the cause of West Nile virus infection can be from blood transfusions, organ transplants, breastfeeding, and even mother-to-baby contact during pregnancy
(see Cause of West Nile Virus). West Nile virus is not spread through casual contact, such as touching or kissing a person with the virus.