Heavy rains followed by the current hot weather has caused the local mosquito population to flourish and the Saint Louis County Department of Public Health is urging all residents to take precautions to help combat mosquitoes and prevent mosquito bites.


“Although serious cases of local mosquito-borne illnesses in humans are rare, it is still important to minimize our exposure,” said Dr. Faisal Khan, director of the public health department. “We can do this by eliminating opportunities for mosquitoes to breed and multiply and by protecting ourselves by using repellants.”

Mosquitos can carry a variety of communicable diseases, including West Nile Virus and Chikungunya, and residents are urged to take the following steps to help keep the mosquito population in check and reduce their chances of being bitten:

  • Remove all standing water: At least once a week, drain water from garbage cans, buckets, toys, flowerpots, wading pools, pet dishes, and other objects that can collect water. Change water in birdbaths at least once a week.
  • Keep gutters cleaned out, and repair any tears in door and window screens.
  • Flexible drainage pipe is commonly used to drain water from downspouts. A big drawback is that it holds water and provides an excellent breeding site for mosquitoes if not properly sloped when installed.
  • Remove unkempt vegetation to eliminate breeding and resting areas for mosquitoes.
  • Wear long-sleeved shirts, long pants, and light colors outdoors.
  • Spray clothing with repellents containing DEET or picaridin.
  • Look for products containing the active ingredient methoprene or Bti (Bacillus thuringiensis israelensis) to place in birdbaths or ponds, to prevent mosquitoes from developing.

The Saint Louis County Department of Public Health’s Vector Control Services Program routinely collects mosquito samples for testing to help determine where to direct control efforts, focusing on those species that carry disease. The program also monitors and treats standing water in public areas as part of its preventative larviciding program. To find out where the county will be spraying, call (314) 615-4-BUG (615-4284) for the nightly mosquito-spraying schedule.

So far this year, there have not been any reported human cases of West Nile Virus in St. Louis County (one mosquito has tested positive). In 2014, there were two reported human cases.

Most people infected with West Nile Virus (70%-80%) do not develop any symptoms. About 20%-30% can experience headache, body aches, joint pains, vomiting, diarrhea, or rash; however, most people with these symptoms recover completely, although fatigue and weakness can last for weeks or months. In less than 1% of cases, symptoms can become much more severe and sometimes include encephalitis or meningitis.

There have been two travel-related cases of Chikungunya reported in St. Louis County this year – both contracted while the patients were travelling outside the area. In 2014, there were three reported cases of Chikungunya – also all travel-related.

Most people infected with Chikungunya will develop symptoms within 3 to 7 days after being bitten by an infected mosquito. The most common symptoms are fever and joint pain, but patients can also experience headache, muscle pain, joint swelling, and a rash. Although the symptoms can be severe, Chikungunya is not often fatal.

Chikungunya can only be transmitted by a mosquito bite. It cannot be transmitted by person-to-person contact. In addition, there are only two species of mosquito that can carry Chikungunya – only one of which is found in the St. Louis area (Aedus albopictus). Currently, the mosquitos in the St. Louis region do not carry Chikungunya.