(MURPHYSBORO, IL) — Health officials in Jackson County say routine mosquito testing has identified the first batch of mosquitoes positive for West Nile virus this year. They were collected Friday near Murphysboro. West Nile virus is transmitted through the bite of a mosquito that has picked up the virus by feeding on an infected bird. Four out of five people who are bitten by an infected mosquito will not experience any illness. Those who do get sick commonly experience fever, nausea, headache and body aches within 3 to 14 days of the bite. However, serious illness such as encephalitis and meningitis, with lingering complications and even death, are possible. Persons older than 50 years of age and those with compromised immune systems have the highest risk of severe illness.