The virus has an incubation period of 5 to 15 days. Most infections are mild and can result in flu-like symptoms such as fever, headache and body aches. Swollen lymph glands may also develop, and in approximately one-half of the cases, a skin rash may occur, spreading from the trunk of the body to the extremities and the head. A more severe infection can be marked by high fever, neck stiffness, stupor, disorientation, tremor, muscle weakness, and rarely, death. The virus interferes with normal central nervous system functioning and causes inflammation and swelling of the brain tissue.
Anyone residing in an area where the virus has been identified is at risk of getting an infection. Those older than 50 years of age have the highest risk for severe disease. The case-fatality rate is highest in the elderly or those with compromised immune systems.
There is no specific treatment for WNV, nor is there a vaccine. In severe cases, intensive supportive therapy is needed, including hospitalization, intravenous fluids and nutrition, airway management, prevention of secondary infections and good nursing care.