Austin, Texas — Under a microscope, a mosquito can look stunning. Their blue-green iridescent scales, purple bands, and attractive spotted wings shimmer — dazzling enough to forget, for a moment, the insect lives to take a sip of your blood.
Mosquitoes range in size, from smaller than your pinky fingernail to a commanding presence in your palm, but it takes a skilled eye and a steady hand to sort the most dangerous species.
At the Arbovirus-Entomology Laboratory of the Texas State Department of Public Health Services, getting a close-up look is a key step in an active statewide effort to keep vector-borne diseases at bay — and alert the rest of the country when a major outbreak is looming.
The US has proved successful in driving away some of the most common mosquito-borne diseases, like malaria and yellow fever, during the 20th century. With less worries about insect-borne illnesses, there are few local and state health agencies in the US investing in active efforts to find and eliminate dangerous insects. Now, these old diseases are starting to creep back in, and new ones are lurking in stagnant puddles, garbage dumps, and culverts. The Centers for Disease Control and Prevention report that the rates of infections spread by animals has more than doubled over the past 20 years. Yet, the picture of these illnesses across the US is spotty at best, and they are likely far more prevalent than we may realize.
However, Texas has been looking out for mosquitoes since 1954, and it’s still a priority. “Texas and Florida are the most vulnerable. … A lot of times, we’re the ones that see the first human cases of emerging diseases because of our climate, the vectors that we have, and the population levels,” said Bethany Bolling, who manages the zoonotic virology group at the Texas state health department. “We have active programs throughout Texas that are weekly collecting mosquitoes. We’re monitoring the population levels. We monitor the species, where they are. And then we’re also looking for pathogens.” The state of Texas spends $755,000 per year on its arbovirus surveillance program and employs seven molecular biologists on the team.
But the US as a whole is not investing enough to contain the threat, and even Texas is scrambling to keep up. This year, West Nile virus, which is mainly spread by mosquitoes from the Culex genus, has been detected in 37 states — including Texas, Massachusetts and Utah — causing at least one death. The CDC has tallied at least 500 cases across the country this year so far.
The US is also contending with a dengue outbreak in Puerto Rico and the US Virgin Islands that began last year. The disease is spread by Aedes mosquitoes, and since 2024, health officials have detected locally acquired cases in Texas, California, and Florida.
There have been at least 60 cases of Chikungunya found in travelers returning to the US this year but no local spread so far. The disease, also transmitted by Aedes mosquitoes, arrived in the Americas in 2013.
The US typically sees about 2,000 malaria cases per year in travelers coming into the country, but in 2023, health officials identified the first locally acquired malaria cases in 20 years in Florida and Texas.
Many of these infections don’t have cures, so preventing them in the first place remains the most effective tactic. Yet, at a time when the US public health system needs more money, staff, and research to stay ahead of these diseases, the Trump administration is pulling it apart, with across-the-board job cuts at the CDC and more targeted cuts aimed at global vector-borne disease monitoring and research into the role of climate change. Federal health officials are also undermining confidence in vaccines, a critical tool that could help limit the damage from vector-borne disease.
And as the researchers in Austin have learned, there’s only so much they can do from the lab.
Containing disease-spreading mosquitoes demands a holistic strategy that includes maintaining natural ecosystems that house natural mosquito predators, improving the housing stock to prevent indoor bites, and training a new generation of insect-borne pathogen specialists to carry on this work.
Texas is an underrated hotspot for vector-borne disease
The words “vector-borne disease” might evoke images of humid, tropical jungles and scenes of poverty. So, Texas might not be the first place that comes to mind. But the state has a long history with these illnesses, and many of the factors that worsen them intersect in the Lone Star State: year-round mosquito weather, rising average temperatures, more severe rainfall, a growing population, plenty of travelers and migrants, and expanding urban and suburban sprawl.
That’s why I was so interested in seeing how Texas is managing these threats and what lessons the rest of the country can learn.
In Austin, the Texas State Department of Health Services operates a laboratory at the northwest corner of town to keep an eye on diseases spread by animals — not just mosquitoes, but ticks, midges, and kissing bugs. (Lyme disease, spread by ticks, is actually the most common vector-borne disease in the US, and the State of Texas tests and tracks ticks, as well). They also monitor diseases, like rabies, that are spread by mammals. Local health departments across the state send suspected insects, bats, and dogs to Austin to see if they’re carrying anything dangerous. “We get animal heads from all over the state for rabies testing,” Bolling said.
Often, the initial outbreaks of vector-borne disease occur in rural or remote areas, and the origins are discovered long after an outbreak is underway. Some cities like Brownsville, right on the US-Mexico border, have built their own in-house system for trapping, tracking, and spraying for mosquitoes.
But most of the Lone Star State’s 254 counties aren’t looking at all. “Only about 20 percent of Texas counties do active surveillance,” said Bolling. “We wish we had eyes on more parts of Texas and knew what mosquitoes were there and what pathogens were circulating.” That means, most often, local officials start collecting vectors after people are already getting sick, and since they don’t have the tools to see what’s being spread, they send their mosquitoes to Austin.
On a map, Bolling pointed out that most of the mosquitoes sent to the lab come from major metro areas like Dallas and San Antonio. “It’s kind of centered around where there’s more people, more money, more resources to participate in our program,” Bolling said. “We offer our test services free of charge, but the [local] programs have to have their own mosquito traps. They have to have people to put them out, and they have to pay to ship us the mosquitoes.” That means some of the more remote and lower-income parts of the state, where outbreaks often start, may not realize what they’re dealing with right away when people start falling ill.
Bolling walked me through two sets of double doors into a series of air-pressure controlled laboratories kitted out with fume hoods, microscopes, and PCR machines. Scientists in lab coats, googles, and gloves carefully took mosquitoes out of minus 80 degree Fahrenheit freezers and sorted them, getting a close look at the species buzzing around from far-flung corners of the state. “We do have beautiful mosquitoes,” said Bolling, who said one of her favorites is Culex tarsalis, which looks like it has racing stripes.
The goal is to put together a picture of which diseases are circulating, which bugs are spreading them, and which tactics could break the cycle.
Why go through all this trouble? Why not just saturate a city in insecticide when an outbreak starts?
For one thing, spraying is expensive, and it’s not always effective. Local governments facing a mosquito outbreak want to make sure they’re spending their limited dollars wisely. Also, mosquitoes can develop a resistance to repeated exposures, kind of like how bacteria can develop resistance to antibiotics. These chemicals can also be detrimental to other insects that are critical pollinators, like bees, or important food for other animals, like bats, so it’s important to tailor the right chemicals to specific mosquitoes in the proper quantities.
There are even some mosquitoes that are “good,” like the Toxorhynchites mosquito, also known as the elephant mosquito. “What’s nice about it, it’s a really large mosquito and it doesn’t feed on humans, so it’s not a concern as far as vector-borne diseases,” Bolling said. Plus, “they’re predacious on other mosquito larvae, so they can be used as a biocontrol.”
Containing mosquitoes requires sophisticated tools — and a new cadre of experts
The mosquito surveillance work in states like Texas, Florida, and California can raise the alarm for the rest of the country during a vector-borne disease outbreak. And by filling in the blanks, scientists hope to find patterns in mosquito disease outbreaks that they can use to predict the next ones.
“We still don’t have good forecasting tools for that, but there do seem to be triggers like shorter winters, earlier springs, and more rainfall, particularly,” said Ben Beard, deputy director of CDC’s Division of Vector-Borne Diseases.
The challenge is acting on warnings, particularly when it comes to a danger that a city or state hasn’t seen before. The public health system tends to be reactive and based on finding already known threats. It’s especially hard for local and state governments to muster the resources to deal with intermittent problems like vector-borne disease outbreaks, where years can go by without big spikes in infection rates. That makes it difficult to secure funding for surveillance, research, and personnel to stay ahead of established perils, let alone deal with invasive mosquito species bringing never-before-seen diseases into new areas.
For instance, PCR tests can amplify the genetic material of a virus in a mosquito sample, but the technique requires knowing a part of the genome of the target. You have to already know what’s in the realm of possibility before you can see if it’s there or not.
To find new, previously unknown diseases spread by mosquitoes, scientists have to do something much more complex: a cell culture assay. That means growing a population of cells and trying to see if there are any germs inside a mosquito that can infect them. It’s an involved and expensive process, and few labs in the US are set up to do it.
But this work is currently paused in Texas. “We’re short-staffed a couple of people right now, so we had to put that on hold,” Bolling said. “It’s unfortunate because that’s an important part of our program.”
The problems for vector-borne disease surveillance aren’t limited by the technology and funding; it’s the expertise. It’s hard to get more people into this career since the job prospects can be spotty. “We need more public health insect researchers,” said Beard, from the CDC.
Erika Machtinger, an associate professor of entomology at Pennsylvania State University, recently helped organize a crash course workshop to train health workers to spot dangerous bugs. In a hotel conference room in Baltimore, Maryland, she and her colleagues invited local health officials from around the country to rotate between stations to identify mosquitoes, ticks, and parasites. They practiced collection methods, like setting up mosquito traps, and went over safety precautions, like tucking pants into socks.
The goal is to help health departments build more connections with their natural environment and understand how changes in forests, wetlands, and deserts can alter the landscape of health risks. “Vector biology surveillance and management training is more necessary now for public health,” Machtinger said.
This is encapsulated in the idea of “one health,” a philosophy that links the integrity of the natural world to human health. In the case of vector-borne disease, the goal is not necessarily to eradicate mosquitoes or disease but to anticipate them and reduce their harm to people. That means spotting dangerous mosquitoes as well as rethinking how we plan neighborhoods, to creating habitats for mosquito predators, to using porous materials to prevent standing water.
It also requires building a more sophisticated operation to proactively look for disease. The CDC set up ArboNET, which it describes as a “passive surveillance system.” “It is dependent on clinicians considering the diagnosis of an arboviral disease and obtaining the appropriate diagnostic test, and reporting of laboratory-confirmed cases to public health authorities,” according to the CDC’s website. “Diagnosis and reporting are incomplete, and the incidence of arboviral diseases is underestimated.” In 2023, the CDC also set up regional training and evaluation centers to build up capacity to anticipate, prevent, and manage vector-borne disease outbreaks.
But, as the need for more mosquito control tactics is growing, resources are drying up. Many state and local governments are facing a cash crunch — not just for public health, but for all government services.
The Trump administration is undermining this work, too, with deep cuts to staffing and budgets across the board in public health, including 2,400 personnel at the CDC, about one-fifth of the agency’s workforce.
The administration has directed much of its ire to research on climate change and public health, drawing down research dollars at the National Institutes of Health for things like developing models for mosquito-borne disease transmission. Officials like US Health Secretary Robert F. Kennedy Jr. are also undermining confidence in vaccines. There are few vector-borne disease vaccines available for US residents, but there are several under development that health officials were hoping could be a key way to contain the danger. Now, those efforts are stalled.
For many local and state health departments, it means they’re on their own when it comes to facing the specter of vector-borne disease. It’s all the more frustrating knowing that many of these problems are manageable with simple interventions like dumping standing water, wearing repellents, and carefully applying insecticides.
Tiny as they may be, mosquitoes are a danger that we can see coming, and the infections they carry can be stopped. Turning a deadly menace into merely an itchy annoyance demands foresight, planning, money, and people dedicated to containing these pretty little biters.
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