CHICAGO - The Chicago Department of Public Health (CDPH) is continuing its effort to protect residents against West Nile virus. Based on an increased number of mosquitoes that carry West Nile virus, CDPH will spray to kill adult mosquitoes in six communities this Tuesday, July 29, 2025 (Austin, Belmont Cragin, and Montclare) and Thursday, July 31 (Beverly, Mount Greenwood, and West Pullman). These are the first spraying events to occur in the city this season.

Weather permitting, the spraying will begin at dusk on July 29 and July 31 and continue through the night until approximately 1 a.m., with licensed mosquito abatement technicians dispensing an ultra-low-volume spray from trucks. Maps of the planned spray zones can be reviewed and downloaded online:

• Tuesday, July 29: Austin, Montclare, and Belmont Cragin
• Thursday, July 31: West Pullman
• Thursday, July 31: Beverly and Mount Greenwood

“Spraying adult mosquitoes is an important part of our effort to protect our communities against West Nile virus. The best way Chicagoans can help prevent disease is through avoidance of mosquito bites in the first place,” said Dr. Janna Kerins, a Medical Director at CDPH.

Each year, CDPH conducts a comprehensive mosquito surveillance, prevention, and control program to protect residents from West Nile virus and other diseases spread by mosquitoes. In addition to spraying, catch basins are treated in the spring to limit the number of mosquitoes that can carry the virus, and traps are placed throughout the city to collect mosquitoes to test for West Nile virus. By identifying locations with the most West Nile virus-positive mosquitoes, the city is able to efficiently target high-risk areas for the virus.

The material being used to control the adult mosquitoes, DeltaGard™, is approved for use by the U.S. Environmental Protection Agency and has been widely applied to control mosquitoes in outdoor residential and recreational areas. The spray will be applied by licensed mosquito abatement technicians from Vector Disease Control International, a leader in the mosquito control industry. Supervisors from the Chicago Department of Streets and Sanitation will guide the crews through the streets.

The spray is not harmful to people or pets and is routinely sprayed in residential areas across the nation. If residents are concerned about the spraying, they can choose to stay indoors and close their windows while it is underway. CDPH staff will be leaving door hangers in the affected areas to notify residents that the spraying will occur.

CDPH reminds residents that the most effective way to prevent West Nile virus is to prevent mosquito bites.

• Use insect repellent that contains DEET, Picaridin, IR3535, or oil of lemon eucalyptus.
• Eliminate standing water. This means emptying water from flowerpots, gutters, pool covers, pet water dishes, and birdbaths regularly.
• Keep grass and weeds short to eliminate hiding places for adult mosquitoes.
• When outside between dusk and dawn, wear protective clothing. This includes long pants, long-sleeve shirts, socks, and shoes.
• Check that all screens, windows, and doors are tight-fitting and free of holes and tears.
• Check on neighbors regularly who may need additional assistance, including the elderly.

West Nile virus cannot be transmitted from person to person. Instead, it is transmitted strictly through mosquitoes. Most mosquitoes do not carry the virus. Additional information on the virus, including symptoms, how to protect against the virus, and recent mosquito testing trends can be found on the CDPH WNV Surveillance Dashboard and the CDPH website.

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