Here's an alert from the Chicago Dept. of Health:
The City of Chicago Department of Health will be spraying to combat West Nile Virus on tonight (Tuesday). Spraying will begin promptly at 7:00 pm and conclude at 2:00 am.
The trucks will be using Anvil, an insecticide approved for use by the U.S. Environmental Protection Agency. The trucks are staffed by licensed mosquito abatement technicians who dispense an ultra-low-volume spray. Residents are advised to keep their families and pets indoors and close their windows while spraying is underway.
Additionally, in the morning following the spraying, you may want to hose down any outdoor furniture or recreation equipment. The Department of Health is also advising residents to drain water from outdoor birdbaths and children's wading pools every four days and beware of old tires, jars, or other containers that may contain standing water.
If you have questions about these efforts, please see our website at http://www.cityofchicago.org/health.