Health & Fitness
4 Human West Nile Virus Cases Reported In Suburban Cook County
Health officials say the risk of human infection is high and are urging residents to take precautions against mosquito bites.
BRIDGEVIEW, IL — Cook County health officials have reported the first four human cases of West Nile virus in suburban Cook County this season as mosquito activity remains high across the region.
All four cases involved adults, according to the Cook County Department of Public Health.
As of the week ending Aug. 22, the risk of human West Nile virus infection in suburban Cook County was considered high, officials said.
Find out what's happening in Chicagofor free with the latest updates from Patch.
The announcement comes after West Nile virus had already been detected in mosquitoes in several parts of northern Illinois this summer.
Patch previously reported that mosquitoes collected in Northbrook tested positive for West Nile virus.
Find out what's happening in Chicagofor free with the latest updates from Patch.
RELATED: West Nile Virus Found In Northbrook Mosquitoes
Positive mosquito samples have also been detected in DuPage and McHenry counties.
Illinois Reports First Human Case
The Illinois Department of Public Health also reported the state's first human West Nile virus case of 2026 this week, involving a Piatt County resident.
West Nile virus is transmitted to people through the bite of mosquitoes that acquire the virus after feeding on infected birds.
Most people who become infected do not develop symptoms, according to health officials.
Others can experience fever, headache, rash and body aches, typically beginning three to 15 days after infection.
More severe cases can affect the nervous system and cause high fever, stiff neck, confusion, muscle weakness and inflammation of the brain or spinal cord. Those illnesses can lead to permanent neurological damage or death.
Cases Rose Sharply Last Year
Suburban Cook County reported 44 human West Nile virus cases and four deaths in 2025, according to the county health department.
Statewide, Illinois reported 150 confirmed human cases last year, more than double the 69 cases reported in 2024.
Ten West Nile virus deaths were reported statewide in 2025, compared with 13 deaths in 2024.
"In light of high West Nile virus activity in Cook County, it is incredibly important for people to protect themselves from mosquito bites," Dr. Kiran Joshi, chief operating officer of the Cook County Department of Public Health, said.
"Using insect repellent, wearing long sleeves and pants, and eliminating standing water around your home can help protect you from mosquito bites."
How To Reduce Your Risk
Cook County's annual "Fight the Bite" campaign recommends four steps to reduce the risk of West Nile virus infection:
- Use an EPA-registered insect repellent. Health officials recommend products containing 20 to 50 percent DEET for adults and 20 to 30 percent DEET for children.
- Eliminate standing water around homes, including in flowerpots, tires, buckets, birdbaths and wading pools.
- Repair damaged window and door screens and make sure they fit tightly.
- Take additional precautions around dawn and dusk, when mosquito activity is often greatest.
More information about West Nile virus prevention is available through the Cook County Department of Public Health.
Get more local news delivered straight to your inbox. Sign up for free Patch newsletters and alerts.
