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West Nile Virus Symptoms

Signs and symptoms of the West Nile virus infection range from no symptoms at all to a rapidly fatal brain infection. In areas where the virus is common, people are more likely to show no symptoms of the infection or have only a mild, flulike illness rather than a severe brain infection. Even in an area of outbreak, the likelihood of a person developing illness after infection with West Nile virus is about 1 in every 140-300 people.

• West Nile virus infection typically begins with the abrupt onset of fever, chills, muscle aches, headache, and overall feeling of illness. Headache is particularly common and may be severe. The person may have sensitivity to light with pain behind the eyes.

• Most people fully recover. In others, particularly the elderly, the disease can progress to cause encephalitis or meningitis.

• In the 59 people hospitalized during the initial New York outbreak, signs and symptoms included fever (90%), muscle weakness (54%), headache (46%), altered mental status (44%), rash (22%), stiff neck (19%), joint aches (17%), sensitivity to light (15%), and body aches (14%).