A bite from a mosquito infected with West Nile virus may transmit the infection. After an incubation period of 1 to 2 weeks, infected female mosquitoe s can then transmit West Nile virus to humans and animals while biting. The mosquitoes and their bites do not differ from the usual bites experienced from uninfected mosquitoes. The incubation period in humans, from the time of infection to the onset of symptoms, is usually 3 to 15 days. Symptoms may appear suddenly and are often characterized by high fever, headache, backache, fatigue, and nausea.
Most people recover from the infection within two weeks.
However it can be fatal, if it develops into encephalitis, especially for the elderly. Anyone living in an area where virus activity has been identified is at risk. Persons over 50 years of age and those with compromised immune systems have the highest risk of developing the most severe of symptoms. To date there is NO vaccine or specific therapy for West Nile infection. Tests are being done with the anti-viral drug ribavirin .