Ill. officials report 1st W. Nile case

September 14, 2009 According to the Chicago Department of Public Health, the patient is a woman in her 70s.

West Nile virus is transmitted through the bite of a mosquito that has picked up the virus by feeding on an infected bird.

So far this year there are three confirmed human cases in Illinois.

Last year, there were 20 human cases, including one death.