Springfield, IL (CAPITOL CITY NOW) – The first human case of a mosquito-borne disease in Illinois for 2026 has been reported.

According to a news release from the Illinois Department of Public Health (IDPH), the human case has been reported in Piatt County. The condition of the person who was infected is not known, but the virus is transmitted to humans from infected mosquitoes.  Symptoms in humans of West Nile are flu-like in nature, including fever, headache, body aches, joint pain, “or other potentially serious complications,” said the news release.

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

In addition, IDPH says three more potential human cases have been identified, so far only described as “probable.”  Those are primarily in Northern Illinois.

While stated above, here is IDPH’s full list of things you can do to prevent West Nile from spreading, or infecting you:

  • REDUCE – 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.
  • Eliminate, or refresh each week, all sources of standing water where mosquitoes can breed, including water in bird baths, ponds, flowerpots, wading pools, old tires, and any other containers.
  • REPEL – when outdoors, wear shoes and socks, long pants and a light-colored, long-sleeved shirt, and apply an EPA-registered insect repellent that contains DEET, picaridin, oil of lemon eucalyptus, IR 3535, para-menthane-diol (PMD), or 2-undecanone according to label instructions.  Consult a physician before using repellents on infants.
  • REPORT – report locations where you see water sitting stagnant for more than a week such as roadside ditches, flooded yards, and similar locations that may produce mosquitoes.  The local health department or city government may be able to add larvicide to the water, which will kill any mosquito larvae. (SOURCE:  Illinois Department of Public Health)

50 Illinois counties have reported mosquito pools, horses, or humans have reported the virus so far this year.  There have been no reports in Sangamon County.  In 2025, there were 73 counties reporting West Nile activity, and 150 human cases.  Ten of those cases were fatal.

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