CHESTER – The Randolph County Health Department is reporting that a mosquito sample collected in the city of Sparta, Illinois has tested positive for West Nile Virus (WNV).
This is the first confirmed positive WNV mosquito sample in the county in 2025.
West Nile Virus is transmitted through the bite of a mosquito that has picked up the virus by feeding on an infected bird. No human cases of West Nile Virus have been reported in Randolph County so far in 2025.
According to data from the Illinois Department of Public Health (IDPH), WNV has been found in 45 counties in Illinois in 2025.
While most people infected with West Nile Virus do not develop symptoms, some may experience mild illnesses such as fever, headache, or body aches. Severe illness can occur in people of any age, however people over 50 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.
There are no vaccines to prevent or medicines to treat WNV infection in people, so the best way to prevent illness from WNV is to avoid mosquito bites.
The Randolph County Health Department urges residents to take the following precautions to reduce the risk of mosquito bites:
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, and apply 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 mosquito breeding grounds – Report areas of stagnant water in roadside ditches, flooded yards and similar locations that may produce mosquitoes.
The Randolph County Health Department will continue mosquito surveillance and testing throughout the season and will provide updates as needed. Residents who experience symptoms such as high fever, severe headache, stiff neck, or confusion should seek medical attention promptly.
For more information about West Nile Virus and prevention steps, please visit the Illinois Department of Public Health website at www.dph.illinois.gov or contact the Randolph County Health Department at 618-826-5007.