CDPH Conducts a Comprehensive Mosquito Surveillance and Control Program to Reduce Threat for Residents

July 15, 2020

First West Nile Virus Positive Mosquitoes in Chicago Reported for 2020

Elena Ivanova

CHICAGO - The Chicago Department of Public Health (CDPH) has confirmed the first West Nile Virus (WNV)-positive mosquito batch in the City for 2020.  CDPH will continue to monitor the area where the mosquito batch tested positive. Following additional tests, CDPH will determine the appropriate next steps to be taken. No human cases of WNV have been reported to date in 2020.

“We are committed to ensuring that all Chicago residents have a safe, healthy and enjoyable summer,” said CDPH Commissioner Allison Arwady, M.D. “Chicago has one of the most robust mosquito control programs in the country. We remain vigilant about protecting residents against West Nile Virus and will continue our surveillance throughout the season.”

CDPH began its annual mosquito control activities on May 26th. This includes treating 40,000 catch basins in Chicago with larvicide, which kills immature mosquitoes and is the most effective control strategy. In addition, CDPH places up to 83 traps throughout the city and tests mosquito samples every week. This information guides CDPH’s efforts throughout the season, allowing teams to respond quickly in specific geographic areas to further reduce risks through neighborhood outreach and spraying.

The most effective way to prevent infection from WNV and other mosquito-borne diseases is to reduce the number of mosquitoes around your home and avoid mosquito bites. Residents are encouraged to take personal precautions against mosquitoes:

  • Use insect repellant that contains DEET, Picaridin, IR3535 or Oil of Lemon Eucalyptus according to label instructions.
  • Eliminate standing water. This includes emptying water from flowerpots, gutters, tires, toys, pet water dishes and birdbaths once weekly.
  • Keep grass and weeds short to eliminate hiding places for adult mosquitoes.
  • When outside between dusk and dawn, wear loose-fitting, light colored clothing, long pants, long-sleeved shirts, socks and shoes.
  • Make sure that all screens, windows and doors are tight fitting and free of holes. Repair or replace screens that have tears or other openings.
  • Check on neighbors regularly, especially those who are older, live alone or need additional assistance.

WNV is transmitted to humans via the bite of infected mosquitoes. Most mosquitoes do not carry the virus. While most people infected with WNV do not feel sick, about 1 in 5 people develop a fever and flu-like symptoms. Severe illness can occur in about 1 in 150 people and is most likely in people over age 60. Because there are no specific antiviral medications to treat WNV in people, the most effective method to prevent infection is to prevent mosquito bites.

For more information about mosquito-borne diseases, including symptoms and prevention, visit

Call 311 to report standing water, dead birds or high grass/weeds.