An adult DuPage County resident has tested positive for West Nile virus, the county's first confirmed human case of 2026.
The DuPage County Health Department confirmed the case Tuesday, Sept. 1, but did not release the patient's identity, age or location, Patch reported. The department's Personal Protection Index, a scale that tracks local mosquito-borne illness risk from zero to three, stood at 2 as of Tuesday. That level indicates elevated risk with confirmed human cases in the county, according to the health department.
The case comes as West Nile virus activity surges across the Chicago metro area. Chicago reported its first two human cases and first death linked to the virus on Sept. 1, Fox 32 reported. Chicago Department of Public Health Commissioner Garth Walker said the unusually rainy summer has given mosquitoes more opportunities to breed across the region. Suburban Cook County confirmed four adult cases around Aug. 28. The Illinois Department of Public Health had already reported the state's first human case of the season the week of Aug. 25, involving a Piatt County resident.
Illinois recorded 150 confirmed human West Nile virus cases in 2025, more than double the 69 cases reported in 2024, according to Patch's Cook County coverage. Ten people died statewide from the virus last year.
Mosquitoes testing positive for West Nile virus were first detected in DuPage County traps as of May 12.
Who is most at risk
No vaccine exists for the virus.
Most people infected with West Nile virus experience few or no symptoms and recover within days, according to the DuPage County Health Department. Mild symptoms include fever, headache, body aches and nausea. Symptoms appear three to 14 days after a bite from an infected mosquito.
People 55 and older with preexisting health conditions face the highest risk of severe illness, which can include high fever, neck stiffness, disorientation, tremors and muscle weakness. The virus does not spread from person to person.
How to protect yourself
The health department urges residents to follow its "Three Rs" prevention steps when the Personal Protection Index is activated:
- Remove containers outside that hold standing water.
- Repel by using insect repellent outdoors and wearing long pants and sleeves at dawn and dusk.
- Report dead birds and standing water that persists more than a week to the DuPage County Health Department at (630) 682-7400.
The department updates the Personal Protection Index every Wednesday at 3 p.m. during surveillance season. The next update is expected Sept. 3.
