Mosquitoes carrying West Nile virus have been discovered in St. Louis County, although no human cases have been reported this year, the county Department of Public Health said Thursday.

“Positive mosquito tests are a reminder that preventative measures are important,” Department of Public Health Director Faisal Khan said in a news release. “Even though serious West Nile virus cases in humans are rare, it is important to minimize our exposure. We can do this by eliminating opportunities for mosquitoes to breed and multiply, and by taking steps to prevent mosquito bites.”

Here are steps residents can take to reduce the opportunities for mosquitoes to breed and multiply:

– At least once a week, eliminate the sources of standing water around a home by draining garbage cans, buckets, toys, flower pots, wading pools, pet dishes and other objects that accumulate and hold water. Turn them over to prevent them from refilling with water.

– Fill any holes in the yard with sand or dirt.

– Drill holes in the bottom of tire swings to allow water to drain.

– Change the water in bird baths at least once a week and keep all gutters cleaned out.

– Treat bird baths and ponds with products containing the active ingredient Bti (Bacillus thuringiensis israelensis) to prevent mosquitoes from developing.

– Ensure that drainage pipes are properly sloped. Flexible drainage pipe is commonly used to drain water from downspouts, but if not properly installed, they will hold water and breed mosquitoes.

Residents can also prevent mosquito bites by doing the following:

– Repair any tears in door and window screens to prevent mosquitoes from entering a home.

– When outdoors, wear long-sleeved shirts, long pants and light-colored, loose-fitting clothing.

– Spray clothing with repellents registered by the U.S. Environmental Protection Agency (EPA) that contain one of the following active ingredients: DEET, picaridin (also called KBR 3023, Bayrepel and Icaridin), oil of lemon eucalyptus, para-menthane-diol, or IR3535. Always follow the directions on the label. Do not use products that contain oil of lemon eucalyptus or para-menthane-diol on children younger than three years old, and never apply insect repellents of any kind to children under two months old.

The St. Louis County Department of Public Health routinely collects mosquito samples to test and help focus its control efforts in areas where high numbers of potential disease-carrying mosquitoes are prevalent and where mosquitoes have tested positive for diseases such as West Nile virus. Its vector control program also monitors and treats standing water in public areas as part of its Integrated Pest Management program. To find out where the county will be spraying, call 615-4-BUG (615-4284) after 5:30 p.m. for the nightly mosquito-spraying schedule.

For more information on mosquito prevention, contact the department’s vector control office at (314) 615-0680 or visit the department’s website at www.stlouisco.com/HealthandWellness/MosquitoControl.