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Posted on: August 24, 2023

West Nile Virus Presence Expands in McLean County

West Nile Virus Presence Expands in McLean County


BLOOMINGTON – A mosquito pool collected by the McLean County Health Department (MCHD) in the 61705 zip code area of west Bloomington has tested positive for West Nile virus (WNV).  A bird sample from the 61701 zip code area of Bloomington submitted to the Illinois Department of Public Health (IDPH) has also tested positive. Staff from MCHD’s Environmental Health division immediately began distributing doorknob hangers in the neighborhoods where these samples were collected to notify residents and provide information on preventative measures.


On July 28, 2023, MCHD also reported that a dead bird tested positive for WNV in the 61761 zip code area in Normal. 


WNV is a mosquito-borne disease that can cause encephalitis, an inflammation of the brain. Culex mosquitoes, also known as house mosquitoes, become infected with the virus by feeding on infected birds. Infected mosquitoes subsequently infect humans and animals.


Mild cases of WNV can cause a slight fever or headache. Severe infections can lead to high fever, disorientation, and even paralysis or death. The Centers for Disease Control and Prevention (CDC) reported 1,035 human cases of WNV and 79 confirmed deaths across the U.S. in 2022. Eight deaths were in Illinois, although none were in McLean County.


“Those who are at highest risk for serious illness are those 50 years of age or older and people with compromised immune systems,” said Angie Crawford, MCHD Senior Environmental Health Practitioner. “Symptoms can occur anywhere from 3-14 days after being bitten by an infected mosquito. Those concerned about symptoms should consider seeking medical attention.”


There is no vaccine for WNV, so the only way to avoid infection is to avoid mosquito bites. To minimize the risks of mosquito-borne illnesses, MCHD recommends following the 3 Rs:


Remove areas of standing water around your yard where mosquitoes can breed, such as old tires or unused planting pots. This is recommended weekly. It takes only 7-10 days for the Culex mosquito egg to develop into a biting adult.


Repel mosquitoes using insect repellent that includes DEET, lemon eucalyptus oil, or picaridin according to label instructions (consult a physician before using repellents on young children). You can also repel by wearing clothing that covers your skin, especially at dusk and dawn when mosquitoes are most active.


Report dead birds that show no sign of injury to the MCHD Environmental Health division at (309) 888-5482. If it appears the bird died within the past 24 hours (no decay or insect infestation) MCHD may collect it and have it tested for WNV.


WNV human infection occurs primarily in midsummer to early fall, although mosquitoes that can carry the disease may be present anytime from Spring to Fall. MCHD’s surveillance of mosquitoes and birds began in May and will continue into October. WNV surveillance and prevention efforts in McLean County are funded by a grant from IDPH. 


For more information on mosquito control strategies, visit:


For more information on WNV, including symptoms, visit:

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