West Nile Virus (WNV) is a mosquito-borne virus that is commonly found in Africa, West Asia, the Middle East, and recently in the United States. The WNV can cause encephalitis (swelling of the brain) and meningitis (swelling of the lining of the brain and spinal cord). Most who are infected with the WNV have no symptoms or experience very mild symptoms. Mild symptoms include a fever, headache, and body aches, occasionally with a skin rash on the trunk of the body and swollen lymph glands. Less than 1% of infected people with WNV will develop severe symptoms. Severe symptoms include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. The onset of symptoms is 3 to 14 days. Symptoms of mild disease will generally last a few days. Symptoms of severe disease may last several weeks, although neurological effects may be permanent.