Illinois confirms first human West Nile virus case of 2026

PIATT COUNTY, Ill. (WMBD) -- The Illinois Department of Health has confirmed the first human case of West Nile virus in Illinois for 2026.

The confirmed case involves a Piatt County resident, according to a release from the department. Three other probable human cases from Northern Illinois have also been identified.

IDPH statistics show that about one in five people who contract the disease caused by an infected mosquito bite may develop common symptoms. This can include headache, body aches, joint pain or other potentially serious complications.

So far in 2026, West Nile virus has been detected in nearly half of Illinois counties with either a mosquito pool, a horse and/or a human from that county testing positive for the virus.

The full list of counties where WNV has been detected can be found here.

In 2025, the virus was found in 73 Illinois counties, according to the IDPH. There were 150 human cases with 10 deaths linked to the virus.

“For many Illinois residents, summer means lots of time spent outdoors enjoying everything our state has to offer,” said IDPH Director Dr. Sameer Vohra.

“Before heading outside, it’s important to take steps to protect yourself and loved ones from mosquito bites and the illnesses they can spread. Applying insect repellent, wearing long, loose clothing, and reporting stagnant water to your local health department can help lower the risk of contracting diseases like West Nile virus.”

The Department of Health reminds people to Fight the Bite by practicing the three R's: reduce, repel and report:

• REDUCE exposure
  • Avoid being outdoors when mosquitoes are most active, especially between dusk and dawn.
  • Make sure doors and windows have tight-fitting screens. Repair or replace screens that have tears or other openings. Try to keep doors and windows shut, especially at night.
  • Eliminate all sources of standing water where mosquitoes can breed, including water in bird baths, ponds, flowerpots, wading pools, old tires and any other receptacles.
• REPEL mosquitoes
  • When outdoors, wear shoes and socks, long pants, and a long-sleeved shirt
  • Apply an insect repellent containing DEET, picaridin, oil of lemon eucalyptus, or IR 3535, according to label instructions. Consult a physician before using repellents on infants.
• REPORT mosquito breeding grounds
  • In communities with organized mosquito control programs, contact your municipal government to report areas of stagnant water in roadside ditches, flooded yards and similar locations that may produce mosquitoes.

The IDPH said West Nile virus is transmitted through the bite of a house mosquito that has picked up the virus by feeding on an infected bird. Common symptoms include fever, nausea, headache and muscle aches. Symptoms may last from a few days to a few weeks.

Most people infected with West Nile virus will not show any symptoms, according to the department. However, in rare cases, it can lead to severe illness including paralysis, meningitis or encephalitis, or even death. People older than 60 and those with weakened immune systems are at the highest risk for severe illness.

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