The human cases have been reported in Chicago, Evanston and several Chicago suburbs.
Illinois health officials say the hot, dry weather is to blame for more mosquitoes infected with West Nile virus this year and an earlier-than-usual first human case of the illness.
Crow found with the disease in Champaign-Urbana on June 12
Chicago crow tests positive
The county did not find West Nile-positive mosquitoes in 2010, but officials say it’s not unusual for Butler County to have at least one vial returned positive during the year.
The county health department says the 12 year-old boy was hospitalized briefly.
One case near Rend Lake
Mosquitoes carrying west Nile like to breed in stagnant water, which is more prevalent in hot, dry conditions.
Mosquitoes with West Nile have been found in communities ranging from Lemay in the southern part of the county to Florissant.