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West Nile virus is a mosquito-borne virus that causes encephalitis (inflammation of the brain) and meningitis (inflammation of the tissues that cover the brain and spinal cord). The reservoir (where the virus normally lives and multiples) is wild birds. This virus was known to be present in Africa, Asia, Europe, and the Middle East, but had not been found in the Americas prior to 1999. Since then, the virus has been found in most states along the eastern coast and east of the Mississippi River. West Nile virus was first identified in birds in Indiana in the summer of 2001.
Mosquitoes transmit the disease to humans by biting an infected bird, and then biting a human. Humans that are bitten by an infected mosquito may show symptoms 3 to 15 days after being bitten.
Most people who get infected with West Nile virus will have no symptoms or mild symptoms. A few individuals will have a more severe form of the disease, encephalitis (inflammation of the brain) or meningitis (inflammation of the tissues that cover the brain and spinal cord).
Symptoms that may be present are: high fever, headache, neck stiffness, muscle weakness or paralysis, and confusion. Most people have very mild disease. West Nile virus has been reported in people ranging from nine months to 94 years old, but more severe disease is likely in individuals over 50 years of age, or those with weak immune systems.
There is no specific treatment, but supportive treatment is provided as with other severe viral illnesses. There is not a vaccine available for humans.
Transmission of West Nile virus can be avoided by preventing mosquito bites, the only know route of transmission. To prevent mosquito bites, wear long sleeves and long pants when out from dusk until dawn, when mosquitoes are most active. Apply insect repellent containing DEET to exposed skin and clothing. Protect your family and your community by reducing the amount of standing water available for mosquito breeding in or near your property. For a more extensive discussion go to ISDH's West Nile Page.