July 21, 2023 – A mosquito trap sample collected in the Sonterra Community of Jarrell, TX has tested positive for West Nile virus. This testing is part of Williamson County and Cities Health District’s (WCCHD) Integrated Vector Management program. The positive test was indicated in lab results received on 7/21/2023 from the Texas Department of State Health Services lab in Austin. 

The positive sample was collected from a trap site near the community pool on Sonterra Blvd. The Sonterra Municipal Utility District has coordinated truck-mounted spraying to occur on the evenings of Sun. Jul. 23 and Mon. Jul. 24, (weather permitting) in the area below. Although the mosquito control product poses no significant health risk, if possible, people and pets may want to stay indoors during spraying.  

Spraying map for Sonterra Community in Jarrell, TX

This is the seventh reported West Nile virus positive trap of the 2023 season in Williamson County. Mosquito samples have been persistently testing positive for West Nile virus for the last six weeks. Health officials continue to encourage use of insect repellent and eliminating standing water. 

Mosquitoes are present in Central Texas year-round, but the population is largest and most active from May through November. During this period, WCCHD monitors the mosquito population and tests for mosquito-borne viruses. 

Symptoms of infection may include fever, headache, and body aches, a skin rash on the trunk of the body, and swollen lymph nodes. Those age 50 and older and/or with compromised immune systems are at a higher risk for severe symptoms, which may include stiffness, disorientation, coma, tremors, vision loss, paralysis, and in rare cases, death.  

Mosquitoes breed in standing water, needing as little as one teaspoon. By draining all sources of standing water in and around your property, you reduce the number of places mosquitoes can lay their eggs and breed. 

What you can do: 

  • WCCHD encourages residents in affected areas to be a part of the solution by eliminating insect breeding areas and larvae before they develop into adult, flying mosquitoes. Standing water can be treated with EPA-approved larvicides that are available for retail purchase.  
  • Larvicides are products used to kill immature mosquitoes before they become adults. Larvicides are applied directly to water sources that hold mosquito eggs, larvae, or pupae. When used consistently, larvicides can help reduce the overall mosquito burden by limiting the number of mosquitoes that are produced, according to the Centers for Disease Control and Prevention (CDC). 
  • Drain standing water in flowerpots, pet dishes, or clogged gutters so mosquitoes don’t have a place to breed and treat water that can’t be drained, 
  • Defend by using an EPA-registered insect repellent, and 
  • Dress in long sleeves and pants when outdoors. 

For more information, go to the WCCHD website at or visit the Texas Department of State Health Services West Nile website at 


The Williamson County and Cities Health District (WCCHD), nationally accredited by the Public Health Accreditation Board, works to protect, promote, and improve the health of all people in Williamson County. WCCHD provides critical public health services including retail food inspections, clinical services like vaccinations and well-woman exams, epidemiological and emergency responses to disease outbreaks, mosquito surveillance, WIC nutrition benefits and education, and administers the county indigent healthcare program. Learn more at