BARTLETT --For the first time this season, mosquitoes have tested positive for the West Nile virus in the Chicago area. The infected mosquitoes were found in DuPage County. A sample was collected in Bartlett. The virus is transmitted to humans and animals through mosquito bites. West Nile can cause fever, headache and body aches and in more serious cases can be fatal. The Illinois Department of Health says this serves as a reminder to protect yourself and your children from mosquito bites this season.