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Mosquitoes trapped in St. Charles County test positive for West Nile

Mosquito biting

During routine trapping this week by the St. Charles County Division of Environmental Health and Protection, a sample from adult mosquitoes has tested positive for the West Nile virus. Officials say there is no cause for alarm, but that this finding serves as a reminder for individuals to remain vigilant in efforts to prevent mosquito bites by wearing repellent when outdoors and to remove standing water from homes and yards.

“Because of the amount of rain we’ve had this season, our staff has done more targeting than usual of known habitat areas,” says Ryan Tilley, Director for the Division of Environmental Health and Protection, “including spraying and water treatment in order to minimize the development of adult mosquitoes. We have been trapping mosquitoes throughout St. Charles County all summer, and this is the first positive result we have had this year. Our plan now is to increase our treatment protocols to control the virus spread. Residents can help by eliminating potential breeding grounds around their homes.”

The Division of Environmental Health and Protection contracts with several county municipalities through its Mosquito Control Program to minimize mosquito populations and decrease the risk of mosquito-borne disease. The program works to control immature and adult mosquitoes by seeking out and eliminating breeding sites and by using biological controls or insecticides. Staff treat common habitat areas to minimize adult and larval populations of mosquitoes.

If you would like to request treatment in your area, and you live in unincorporated St. Charles County or within the city limits of Augusta, Cottleville, Dardenne Prairie, Flint Hill, Lake Saint Louis, Portage des Sioux, St. Paul, Weldon Spring, Weldon Spring Heights and Wentzville, please use our online treatment service at If you live within the city limits of O’Fallon, St. Charles or St. Peters, please contact your city hall regarding mosquito abatement and local spraying efforts.

To minimize exposure to mosquito bites and related illnesses residents should follow these precautions:

  • Use insect repellent containing DEET, picaridin, IR355 or oil of lemon eucalyptus according to manufacturer’s guidelines when outdoors. Remember to apply sunscreen first, let it dry, and then apply repellent. Reapply repellent as necessary.
  • Wear long sleeved shirts and pants and consider treating clothing with permethrin products.
  • Limit time outdoors when mosquitoes are most active – dusk and dawn.
  • Once a week, empty and scrub, turn over, cover, or throw out items that hold water, such as tires, buckets, planters, toys, pools, birdbaths, flowerpots, or trash containers.

About West Nile Virus

According to the Centers for Disease Control and Prevention, 36 states — including Missouri and Illinois — have reported West Nile virus activity (as of Aug. 6). Human cases of West Nile virus usually display symptoms such as fever, headache, body ache, vomiting, and rash. For additional information on the West Nile virus, please visit

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