What proportion of people infected with West Nile virus become severely ill?
About four out of five people infected with West Nile virus will not have any symptoms. About one out of five will develop the mild symptoms of West Nile fever: fever, headache, and body aches. Occasionally there will also be a skin rash on the trunk of the body and swollen lymph glands. About 1 in 150 people infected with West Nile virus develop the more severe symptoms of West Nile encephalitis or meningitis: headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. Mortality occurs in 3 – 15% of cases with severe symptoms.
