An adult DuPage County resident has tested positive for West Nile virus, marking the county's first confirmed human case of 2026.
The DuPage County Health Department announced the case on Tuesday, Sept. 1, in a press release reported by NCTV17. The department did not release the patient's age, location within the county or health status.
The announcement came the same day the Chicago Department of Public Health reported the state's first West Nile death of 2026, along with two additional human cases in Chicago. Cook County had reported four human cases as of Aug. 28, according to Patch.
Protection index at moderate level
The health department's Personal Protection Index, a weekly gauge of local West Nile activity on a 0-to-3 scale, stood at 2 as of Monday, Aug. 31. The department described that level as moderate, driven by the confirmed human case and a large number of infected mosquitoes in the area. The index updates every Wednesday.
"While most people won't experience serious symptoms, West Nile virus can lead to severe illness in high-risk groups such as older adults, individuals with chronic medical conditions, and immunocompromised persons," Illinois Department of Public Health Director Dr. Sameer Vohra said in a state news release.
About one in five people infected with West Nile develop flu-like symptoms, including fever, headache, body aches and nausea, according to the CDC. Symptoms typically appear three to 15 days after infection. Less than 1% of cases affect the central nervous system and can result in hospitalization or death.
Virus detected locally in May
West Nile virus was first detected in the area in May. Clarke Mosquito Control confirmed the virus in a mosquito sample collected near St. Charles Road and Westgate Drive in Carol Stream on May 22. The Village of Carol Stream said at the time that no human cases had been reported, and a localized mosquito control application was applied May 26.
The Wheaton Mosquito Abatement District covers 23 square miles, including sections of Carol Stream and Glendale Heights.
The risk is not new. Illinois reported 150 confirmed human West Nile cases in 2025, more than double the 69 cases in 2024. Ten people died statewide from the virus last year.
How to protect yourself
The health department is urging residents to follow what it calls the "3Rs of defense":
- Reduce mosquitoes by eliminating standing water around homes and keeping window screens intact.
- Repel with an EPA-registered insect repellent containing DEET.
- Report spots in public areas where water has been pooling for more than a week.
Officials also recommend wearing long sleeves and pants outdoors and being especially cautious between dusk and dawn, when mosquitoes are most active.
Residents can reach the DuPage County Health Department at (630) 682-7400 or visit dupagehealth.org for updates.
