Mosquitoes are back in North Texas — and so is West Nile virus, the infectious disease carried by these tiny bloodsuckers.
In recent weeks, Dallas County Health and Human Services confirmed mosquitoes collected from traps in Cedar Hill, DeSoto, Dallas, Farmers Branch and University Park were positive for West Nile. Positive samples were also confirmed in Mesquite and Irving. In neighboring Tarrant County, the first positive sample of the season was confirmed on May 14.
Warmer weather typically heralds the start of mosquito season, which brings a heightened risk of diseases such as West Nile. A West Nile outbreak in North Texas in 2012 caused more than two dozen deaths and more than 350 cases.
Here’s what to know about how to protect yourself from mosquitoes, what local government agencies are doing, what other mosquito-borne illnesses have been found in Texas and which mosquitoes live in the state.
How to prevent and repel mosquitoes
Mosquitoes can be present all year — depending on where you live in Texas — but they are usually most active when the weather is warm and humid. These weather conditions provide rainfall that most mosquitoes need to lay their eggs.
To prevent your home from becoming a mosquito motel, the city of Dallas recommends dumping or draining anything that can collect water or rotting organic matter, which provides nutrients for mosquito larvae. Such containers include buckets, bird baths and potted plants.
Only adult female mosquitoes bite, and they do so to get a blood meal for their eggs. Their bites can transmit disease. Here are some tips for protecting yourself:
- Use insect repellent containing DEET or other Environmental Protection Agency-registered repellents when outside.
- Wear long sleeves and pants, preferably loose-fitting, light-colored and treated with insecticide.
- Limit your time outdoors from dusk to dawn when mosquitoes are most active.
How local agencies are fighting mosquitoes
North Texas governmental agencies, some working with private mosquito control companies, set traps all over their municipalities. The traps are routinely monitored and mosquitoes are collected and tested for infectious diseases, typically West Nile, said Christian Grisales, public information officer for Dallas County Health and Human Services.
If the samples are positive, EPA-approved insecticide is sprayed in the affected areas, Grisales said.
In Tarrant County, traps are checked and tested daily, said Edrea Au, senior public information officer with Tarrant County Public Health, in an email. The county has a mosquito dashboard where residents can see which traps have tested positive. As in Dallas County, insecticides are sprayed if a positive sample is found.
Mosquito-borne illnesses in Texas
West Nile has been a leading threat of mosquito-borne disease in Texas since its arrival in 2002. The largest West Nile outbreak in the state, in 2012, caused nearly 2,000 cases and more than 80 deaths.
There are other mosquito-borne illnesses that have been found in Texas.
A Zika outbreak in 2016 caused 315 cases in the state, including more than a dozen in Dallas County. The virus usually results in mild symptoms, but it can cause severe birth defects. Only one Zika case has been reported in Texas in the last four years.
In 2023, Texas had its first locally acquired case of malaria in 30 years. The case occurred in the south of the state.
Another illness, called dengue, has been historically rare in Texas but saw a surge of cases in 2023.
The mosquitoes of Texas
There are more than 80 species of mosquitoes in Texas, with more than 50 calling North Texas home, KERA reported in 2016.
Most mosquito-borne infections are spread by mosquitoes from three genuses — Aedes, Culex and Anopheles — that are found in North Texas. These mosquitoes feed off humans and animals, with the exception of Aedes aegypti, the yellow fever mosquito, which prefers human blood.
Aedes mosquitoes — sometimes called “ankle biters” — can carry Zika, West Nile and dengue. Anopheles mosquitoes can carry malaria, and Culex mosquitoes can transmit West Nile. In Denton, a Culex mosquito called the southern house mosquito has often tested positive for West Nile in recent years, according to the city’s 2019 Mosquito Surveillance and Response Plan.
After the severe storms North Texas experienced in recent weeks, you might have noticed what seem like monster-sized mosquitoes. These are floodwater mosquitoes, an aggressive variety that can grow as large as 1.5 inches, compared to a quarter inch for other species, Sonja Swiger, an entomology professor at Texas A&M University AgriLife, told The News in 2022.
Floodwater mosquitoes bite humans, but they prefer large mammals such as cows and horses. They do not carry West Nile or other infections.
Miriam Fauzia is a science reporting fellow at The Dallas Morning News. Her fellowship is supported by the University of Texas at Dallas. The News makes all editorial decisions.