Mosquito trucks will roll through the Hinsdale area Friday night after the Clarendon Blackhawk Mosquito Abatement District declared that West Nile virus levels in the local mosquito population have reached the threshold for likely human transmission.
The District announced the emergency adult mosquito control operation on Tuesday, Aug. 4. Spraying is scheduled for Friday, Aug. 7, between 9 p.m. and 1 a.m., weather permitting, according to a press release posted on the Village of Clarendon Hills website.
The operation marks an escalation from the larval control program the District has run since early May. The District called it a "contingency" measure triggered by elevated virus levels detected in trapped adult mosquitoes.
What residents should know before Friday
The District warned that the mosquito species carrying West Nile virus is a passive, non-aggressive biter whose presence often goes undetected. Residents may not realize they're being bitten, making precautions more important than the usual summer swatting suggests.
Recommended steps:
- Avoid outdoor activity around dusk, particularly Friday night during the spray window.
- If outdoors, wear shoes, socks, long pants and a long-sleeved shirt. Loose-fitting, light-colored clothing works best.
- Use insect repellent according to the manufacturer's instructions.
- Eliminate standing water around the home. Bird baths, wading pools and similar containers should be emptied or changed at least once a week. Keep screens on rain barrels in place.
People with respiratory conditions should stay indoors and close windows during the spray application.
About the insecticide
The District will apply Zenivex E4, manufactured by Wellmark International of Schaumburg, at a rate of 0.00350 pounds of active ingredient per acre. The active ingredient is etofenprox, a non-ester pyrethroid the U.S. Environmental Protection Agency has classified as a reduced-risk pesticide. According to the product's EPA registration label, it is approved specifically for controlling mosquitoes that carry West Nile virus.
The chemical presents minimal risk to humans and pets, biodegrades rapidly in sunlight and is applied after sunset. Buffer zones are maintained around fish habitat because etofenprox is toxic to aquatic life.
Statewide context
The Hinsdale-area alert follows a broader pattern across Illinois this summer. Communities in Kane County, including Geneva and St. Charles, conducted their own West Nile-triggered spray operations in late July, according to the Kane County Chronicle.
In 2025, Illinois recorded 150 confirmed human cases of West Nile virus and 10 deaths statewide, according to the Illinois Department of Public Health. Most infections cause mild flu-like symptoms, but in less than 1% of cases the virus can lead to meningitis, brain swelling, seizures or paralysis, particularly among older adults.
Two layers of mosquito control
The Village of Hinsdale also maintains its own mosquito abatement contract. Trustees approved a three-year, $58,300 deal with Clarke Environmental Mosquito Management of St. Charles earlier this year for catch basin treatment, larval monitoring and a resident hotline. The Clarendon Blackhawk District operates as a separate taxing body covering properties in and around Clarendon Hills and the surrounding area, including the Hinsdale area.
The spray is weather-dependent. The District's larval control program will continue through October, but no follow-up spray date has been announced. Residents can check clarendonhills.us for updates.
