Each year during the mosquito breeding season the Forest Preserve District monitors dozens of aquatic sites for Culex mosquitoes, the genus known to transmit West Nile virus. If it finds mosquitoes that test positive, it treats the water with a naturally occurring bacterium that kills Culex larvae. It also treats over 320 catch basins with an extended-release larvicide to prevent larvae from developing into adults.

Each week the District shares its findings with the DuPage County Health Department and the Illinois Department of Public Health. Use the links below to find the latest statistics and prevention tips, and watch our video to learn more about how we monitor mosquitoes in the preserves.