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DuPage County— The DuPage County Health Department (DCHD) has confirmed the first mosquitoes to test positive for West Nile virus (WNV) this year in DuPage County. The first positive pool of mosquitoes was collected on June 30, 2021, in Clarendon Hills, and the second positive pool was collected on July 1, 2021, at the Waterfall Glen Forest Preserve in Lemont. DuPage County health officials encourage residents to take steps to protect themselves from mosquito bites and the risk of contracting WNV.

“We encourage you to Fight the Bite to protect yourself and your family from West Nile virus by preventing mosquito bites,” said Karen Ayala, DuPage County Health Department Executive Director. “Let’s take the time to remove standing water around our homes and use insect repellant when spending time outdoors.”

This year, there have been no reported human cases of WNV in DuPage County to date. However, the identification of a positive mosquito pool is associated with an increased risk of WNV in people. Additionally, the recent hot, dry weather is an ideal environment for mosquitoes (primarily Culex mosquitoes) that spread WNV.

Last year, the first mosquitoes to test positive for West Nile virus were collected on June 30, 2020, in Naperville.

To Fight the Bite this summer, practice the “4 Ds of Defense”:

  • Drain: Drain those items that collect standing water around your home, yard, or business. Scrub and refill pet water dishes and birdbaths regularly.
  • Defend: Use an insect repellent containing DEET when outdoors and reapply according to directions.
  • Dress: Wear long pants, long sleeves, and closed-toe shoes when outside to cover the skin.
  • Dusk to Dawn: Wear repellent outdoors during these prime times for mosquito activity.

Residents may also report dead birds on the Health Department’s website by accessing the Citizen Reporter and clicking the Health Reporter option to submit their report. Dead birds can often be an early sign of the presence of WNV in the environment.

The Personal Protection Index (PPI) widget provides residents with a real-time snapshot of WNV activity in the county, which ranges from zero to three, zero meaning there is no risk, and three announcing a high level of risk with multiple confirmed human cases of WNV. The widget is based on guidance from the Centers for Disease Control and Prevention and the Association of State and Territorial Health Officials. Residents will be able to see the PPI widget by visiting

Many community partners, including townships, municipalities, and park districts, have the PPI widget posted to their homepages. Residents who click on the widget will be linked to the Health Department’s “Fight the Bite” page for prevention tips.

The Health Department monitors WNV activity by collecting and testing mosquitoes in traps located throughout the county. The PPI widget will be updated by 3 p.m. each Wednesday throughout the WNV season. These weekly updates will be determined by the Health Department’s vector-borne disease surveillance experts.

WNV activity generally decreases in the fall when cooler temperatures arrive and especially after the first frost of the season.