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The original item was published from 8/18/2021 9:16:33 AM to 10/17/2021 12:00:03 AM.

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SCCMO Health Press Releases

Posted on: August 18, 2021

[ARCHIVED] Surveillance Detects West Nile Virus in St. Charles County Mosquitoes

St Charles County Mosquito Control staff completing treatment at boat dock along Mississippi River.

August 18, 2021

ST. CHARLES COUNTY, MO – Routine trapping and surveillance by the St. Charles County Division of Environmental Health and Protection’s Mosquito Control program has detected positive test results for West Nile virus from mosquitoes within the county. There have been no positive cases of West Nile in humans reported this year. Program staff notes there is no reason for alarm from these findings but reminds residents to remain vigilant with efforts to prevent mosquito bites by wearing repellent when outdoors.

“Our staff has been aware of the presence of West Nile virus around the metropolitan area and has been trapping and testing mosquitoes all summer,” says Seth Otto V, Mosquito Control Program Coordinator. “Following this positive indication in our community, our staff will increase treatment efforts aimed at reducing the risk for exposure to residents. Staff also reminds residents about the importance of taking steps to ‘Block the Bite’ whenever outdoors this summer and fall.”

This is the fifth consecutive year that St. Charles County has utilized collection traps to analyze mosquito populations. Traps have been placed in various locations throughout the county since June and will remain in place through September. Staff checks traps and analyzes collected mosquitoes on a weekly basis to determine the presence of various insect species and incidences of the virus.

“By using information from these collection sites, our staff can target areas with specific recommended treatment activity,” notes Otto. “Different species of mosquito behave differently, so knowing the species at a location enables our staff to be more effective in controlling mosquito-borne disease.” 

What Should Residents Do to “Block the Bite”?

To minimize exposure to mosquito bites, Mosquito Control staff recommends residents:

  • Use insect repellent when outdoors. Repellents containing DEET, picaridin, IR3535 or oil of lemon eucalyptus are proven to provide protection when used according to manufacturer’s recommendations. When also using sunscreen, apply the sunscreen first, let it dry, and then apply repellent.
  • Limit time outdoors when mosquitoes are most active – during dusk and dawn hours.
  • Wear light-colored, long-sleeved shirts and long pants when in traditional mosquito habitat such as wooded areas or tall grass.
  • Drain areas around the home that may hold water for five days or longer. Common sites include clogged gutters, pool covers, potted plant, bird baths and tire swings.

What Does St. Charles County Do to Prevent Nuisance Mosquito Populations?

The Division of Environmental Health and Protection contracts with several St. Charles County municipalities to investigate and control mosquito populations. Mosquito Control staff monitors for larval and adult insect activity, sets traps to test for the presence of different species and the diseases they may carry, and shares information on the most effective methods for protecting the public. The Mosquito Control staff also treats habitat areas to prevent larvae from developing into adult insects and performs targeted spraying in areas where a high population of disease-carrying or nuisance mosquitoes is observed.

Residents who live in unincorporated St. Charles County or within the city limits of Augusta, Cottleville, Flint Hill, Lake Saint Louis, Portage des Sioux, St. Paul, Weldon Spring, Weldon Spring Heights and Wentzville should use the CitizenServe online portal at to request treatment by Mosquito Control staff. Those who wish to add their address to a “No Spray” list can call 636-949-1800. Residents living within the city limits of Dardenne Prairie, O’Fallon, St. Charles and St. Peters should contact their respective city halls for treatment concerns.

About West Nile Virus

West Nile virus is spread by the bite from an infected mosquito and is the leading cause of mosquito-borne illness in the United States. According to the Centers for Disease Control and Prevention, more than one-half of the continental U.S. — including Missouri and Illinois — has reported West Nile virus activity in local insect populations or other animals this year. While most people infected with West Nile virus do not feel sick, approximately 1 in 5 display symptoms such as fever, headache, fatigue, body ache, vomiting and rash, and 1 in 150 can develop serious illness, including death. Individuals over the age of 60 and those with certain medical conditions are at greater risk for developing severe illness. Individuals who experience symptoms should seek medical care.


CONTACT: Doug Bolnick, Public Information Officer, 636-949-7408

About the St. Charles County Division of Environmental Health and Protection

The Division of Environmental Health and Protection works with residents, area businesses and local organizations to promote healthy conditions in St. Charles County. Division staff conducts facility inspections, collects recyclable material and provides mosquito control treatment across the county to prevent the spread of disease. To learn how the division helps to ensure the community’s well-being, visit or call 636-949-1800.

About the St. Charles County Department of Public Health

Through the efforts of its three divisions — Environmental Health and Protection, Health Services and Humane Services — the St. Charles County Department of Public Health provides a wide range of services that enhance the well-being of a community that ranks among the healthiest counties in Missouri. To learn how the department assists this region or to find out about volunteer opportunities with any of the divisions, visit or call 636-949-7400.

About St. Charles County

Founded in 1812, St. Charles County is one of the fastest growing counties in Missouri. With a population of 407,056, it is the state’s third largest county. It is home to 17 scenic county parks, encompassing nearly 4,000 acres with additional land under development and more in reserve for future development.

With one of the largest economies in the state, St. Charles County is home to several multi-national companies, including General Motors, Citi, MasterCard Worldwide and Boeing. It is ranked among the top 25 counties in the nation in high-tech job growth by the Progressive Policy Institute and consistently has the lowest unemployment rate in the Metropolitan St. Louis area.

St. Charles County has more than 1,170 employees in more than 30 departments and offices, who work to make the county an excellent place to live, work and shop. For more information, visit

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