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DuPage County Health Department News

Posted on: July 11, 2023

First Mosquitoes Test Positive for West Nile Virus in DuPage County

A Mosquito on a Leaf

DuPage County — The DuPage County Health Department (DCHD) has confirmed the first mosquito batches to test positive for West Nile virus (WNV) this year in DuPage County.

The first WNV-positive pools of mosquitoes were collected on July 5, 2023, in Medinah, Wheaton, and Wood Dale. County health officials encourage residents to take steps to protect themselves from mosquito bites and the risk of contracting WNV. Last year, the first mosquitoes to test positive for West Nile virus were collected on May 24, 2022, in Roselle.

“This summer, take action to protect yourself and your family from West Nile virus by preventing mosquito bites,” said Adam Forker, DuPage County Health Department Executive Director. “Fight the Bite when spending time outdoors by using insect repellent, draining standing water, and limiting outdoor exposure from dusk to dawn.”

This year, there have been no reported human cases of WNV in DuPage County to date. However, the identification of positive mosquito pools 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.

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.


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Residents may also report dead birds on the Health Department’s website. Dead birds can often be an early sign of the presence of WNV in the environment.

DCHD’s 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 is 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. Additional statewide information and data can be found at the Illinois Department of Public Health’s West Nile virus website and the West Nile virus Dashboard.


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