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Dallas County Health and Human Services (DCHHS) confirmed this week that two mosquito pools in Farmers Branch (ZIP 75234) and one in Dallas (ZIP 75244) have tested positive for West Nile Virus, marking the first detections of the 2026 season in the area.
No human cases have been reported in Farmers Branch or Dallas County. All three cities covered by the Branch Herald have active mosquito management programs underway, though their response protocols differ.
Farmers Branch treats public water sources, storm drains, detention ponds and other municipal infrastructure, with bacterial larvicide (mosquito dunks and granules) as its primary prevention tool. The city is not planning ground spraying at this time and would only do so if a human case of West Nile is confirmed within city limits. The emphasis is on stopping mosquitoes before they hatch. The city also distributes free mosquito dunks to residents.
Addison is distributing free mosquito dunks and repellent to residents (see sidebar) and monitoring for positive pool results. No Addison pools tested positive in this week’s DCHHS report. When a positive test result comes in, the city responds by spraying the following two mornings.
Carrollton uses ground spraying with a permethrin-based product when mosquito pools test positive for West Nile. Spraying is applied under low-wind conditions and restricted to areas around positive detections. Officials say the method is safe for residential neighborhoods when used as directed. The city also identifies and treats breeding sites with larvicide (mosquito dunks).
West Nile Virus is the leading cause of mosquito-borne disease in the continental United States. It spreads primarily through the bite of an infected Culex mosquito, the common “house mosquito,” which picks up the virus by feeding on infected birds.
The reassuring news: most people who contract the virus never know it. According to DCHHS, roughly 80 percent of infected individuals show no symptoms at all.
About one in five will develop West Nile fever, headache, body aches, fatigue, and sometimes a rash, that typically resolves within a few days.
The serious cases are rare but real. Approximately one in 150 infected people develops neuroinvasive disease, which can include encephalitis, meningitis, muscle weakness, tremors, paralysis, and in rare cases, death. Older adults and people with weakened immune systems face the highest risk of severe illness.
There is no vaccine and no specific treatment. Care is supportive.
Statewide context adds some urgency to the early detections: Texas recorded 127 human West Nile cases in 2025, and the virus has been endemic in the state since 2002. Historically, case counts climb from May through October as temperatures rise and mosquito populations peak.
Dallas County reported 37 cases of human West Nile fever and three deaths in 2024. The county reported 10 cases and 1 death in 2025.
All three cities are urging residents to follow the “4 Ds” promoted by DCHHS:
Make sure window and door screens are in good repair and check your yard after every rain, new standing water can appear quickly.
If you develop a sudden high fever, severe headache, stiff neck, disorientation, muscle weakness or vision changes after possible mosquito exposure, see a physician promptly. West Nile is diagnosed through a blood test, and early medical attention matters for severe cases.
DCHHS deploys hunderds of traps weekly to monitor mosquito activity countywide throughout the season.
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