First Human Case of West Nile Virus Detected in Will County in 2026

JOLIET, Ill. – The Illinois Department of Public Health (IDPH) announced the first human case of West Nile Virus (WNV) in Will County. A 51-year-old person from Will County has tested positive for West Nile Virus after developing symptoms in the second week of August. The individual has not required hospitalization and is recovering. The Will County Health Department’s Environmental Health Division has also reported that mosquito batches in seven different Will County communities have tested positive for WNV this summer.

IDPH reported a total of 24 human cases of WNV have now been detected throughout the state. In addition to the case in Will County, 15 were reported in Cook County, two were reported in DuPage County while Kane, Kendall, Livingston, Madison, Piatt, and Shelby all reported one positive case. IDPH has also reported two deaths have been linked to WNV.

So far in 2026, there have been 2,773 WNV-positive mosquito batches from 52 counties throughout the state. In Will County, mosquitoes trapped in Crete, Frankfort, Bolingbrook, Plainfield, Joliet, and Mokena have tested positive for WNV this summer.

WNV typically causes mild, flu-like symptoms. According to the Centers for Disease Control and Prevention (CDC), most people [8 out of 10] infected with West Nile virus do not develop any symptoms. About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people who develop symptoms from WNV recover completely, but fatigue and weakness can last for weeks or months.

However, according to the CDC, about 1 in 150 people who are infected develop a severe illness that affects the central nervous system such as inflammation of the brain (encephalitis) or inflammation of the membranes that surround the brain and spinal cord [meningitis). Severe illness can occur in people of any age, however people over 60 years of age are at greater risk for severe illness if they are infected. People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.

Because there is no vaccine available to prevent West Nile virus, it is important to avoid mosquito bites.

“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 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.”

IDPH encourages the public to Fight the Bite by practicing the three “R’s” – reduce, repel, and report:

• 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, or IR 3535 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.