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........

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