Symptoms of West Nile fever may include fever, headache, achy muscles, and extreme tiredness, perhaps with skin rash and swollen lymph glands. In a fraction of cases, the fever leads to encephalitis, which is fatal in some cases or may cause neurologic after-effects. There is no vaccine against West Nile, and no known cure. As with other viral diseases, treatment consists of support until it has run its course. The incubation period the time between an infectious bite and the onset of symptoms is usually 5-15 days.
Humans get the West Nile Virus largely from the bite of mosquitoes.
Although some 150 species of mosquitoes are found in the United States, the primary transmitter of West Nile is Culex pipiens. The female mosquito catches the virus when it bites an infected bird, and can then pass it along if it later bites a human. Humans do not get it from other humans or animals. The virus can infect many different species of birds and other animals, but crows seem particularly vulnerable, and monitoring programs focus on them. In fact birds were the key to solving the 1999 outbreak.