Denton city leaders issued an alert Thursday after a sample of mosquitoes collected Aug. 18 from traps located near Unicorn Lake tested positive for West Nile virus.

“These are the first samples that have tested positive for West Nile virus in the city of Denton this year,” said Ken Banks, the city’s environmental services director, in a news release.

The incidence rate of West Nile virus in mosquitoes has been low this year compared with the last couple of years, Banks said. By this time last year four traps had captured mosquitoes with the virus.

The finding near Unicorn Lake in southeastern Denton caused the city to enter Risk Level 3 of its mosquito surveillance and response plan. Level 3 means the probability of a person contracting a mosquito-borne disease like West Nile is low to moderate. Also, the amount of biological agents applied to kill mosquito larva is increased over Level 2 amounts.

The city will continue to conduct routine surveys of adult mosquitoes, which will be identified to species level and screened for the presence of viruses. The locations where disease-carrying mosquitoes were captured will be indicated on a map available on the city’s website at www.cityofdenton.com.

Although West Nile virus infections are rare in humans, personal protection is important at this risk level, especially for the elderly and children. Residents can try to avoid exposure to the virus and other mosquito-borne diseases by following these tips:

• When outdoors, use mosquito repellent containing DEET or Picaridin. Mosquitoes often are most active at dusk and dawn. Consider wearing long sleeves and pants or staying indoors during these times.

• Eliminate mosquito breeding sites by emptying areas of standing water and replacing water in pet dishes and birdbaths regularly. Drill holes in tire swings to allow water to drain. Empty children's wading pools and place them on their sides until you plan to use them.

• Install or repair screens on windows and doors.

• Use BTI briquettes, floating rings that kill mosquito larvae, in standing water. Denton residents can pick up briquettes (limit two per resident) from 8 a.m. to 5 p.m. weekdays at the utilities service center, 901A Texas St., or from 7 a.m. to 3 p.m. Saturdays at the city composting operations at 1100 Mayhill Road.

The following websites offer more information on mosquitoes:

• Texas Department of State Health Services: www.dshs.state.tx.us  

• Denton County Health Department: www.dentoncounty.com/heart

For information on the city’s mosquito surveillance and response plan, call the Water Utilities Department at 940-349-7150.