Clinical manifestations in humans

The incubation period is usually 2- 14 days. Eighty per cent (80%) of infected people are totally asymptomatic (the disease runs subclinically). About 20% of infected people develops the so called "West Nile fever" (WNF); symptoms remind us of flu that last less than a week: fever  headache tiredness body aches nausea, vomiting lymphadenopathy skin rash on the trunk of the body (occasionally) In less than 1% of infected people, a neuroinvasive form of the disease (WNND) may occur (encephalitis/meningitis/acute flaccid paralysis) and the main symptoms/signs are the following: headache high fever neck stiffness stupor disorientation coma tremors convulsions muscle weakness paralysis   People over the age of 50 and immunocompromised persons (e.g. HIV, transplant patients) are at the highest risk for getting severely ill when infected with WNV. It is estimated that for every neuroinvasive case, another 150 non-neuroinvasive cases take place.