The Daily Populous Monday August 18th, 2025 morning edition
Authored by nbcnews.com and submitted by ARandom_RedditUser

LAS VEGAS — If at one time it was thought mosquitoes couldn’t survive in desert climates, this city is a case study in how wrong that is.

Mosquitoes typically prefer more tropical, humid conditions, but these biting machines have exploded in number throughout the Las Vegas Valley in recent years because of a host of changes.

A mix of urban development, climate change, insecticide resistance and genetic adaptations are creating a more hospitable environment for the insects in southern Nevada.

Las Vegas is hardly alone in its battle against the pesky insects. Warmer temperatures and shifting weather patterns are expanding the geographic range in which mosquitoes live and breed. In many ways, what’s happening here is playing out across the desert Southwest and beyond.

The mosquitoes have brought with them not only the nuisance of bug bites, but also the major threat of mosquito-borne diseases such as dengue fever and West Nile virus to Las Vegas and the rest of Clark County.

It's also caught people off guard.

“People aren’t wrong that mosquitoes shouldn’t really thrive in desert conditions, but it’s clear that the particular set of species that we do have in Clark County has adapted to the local ecology,” said Louisa Messenger, an assistant professor in the department of environmental and global health at the University of Nevada, Las Vegas.

The species that have taken hold in Clark County include Culex mosquitoes, which can carry West Nile virus, and Aedes aegypti mosquitoes, the primary spreaders of dengue. What’s more, Messenger and her colleagues at UNLV have found that mosquitoes in Las Vegas are becoming resistant to insecticides, a major public health risk in a city built on tourism.

“It is a little bit of a ticking time bomb,” Messenger said.

She has for some time been concerned about how vulnerable Las Vegas is to mosquito-borne diseases. In particular, dengue has been surging in North America and South America, with more than 13 million cases recorded across the continents in 2024, according to the Centers for Disease Control and Prevention.

“In Vegas, we have more than 48 million visitors coming through our doors every year from all over the planet,” Messenger said. “It just takes a couple of mosquito bites to start local transmission.”

Last year, there were 26 reported cases of West Nile virus in humans in Las Vegas, according to the Southern Nevada Health District, trailing the city’s largest outbreak of 43 cases in 2019. Yet, in 2024, scientists still found a record number of mosquitoes that tested positive for the virus in and around the city, which suggests the risk of exposure was very concerning.

This year, the public health department hasn’t identified any human cases so far, even as mosquitoes have tested positive for the virus in certain ZIP codes. Messenger said it’s not well understood what specific factors fuel outbreaks in some years and not in others.

“We see these overlapping factors but they are quite difficult to tease it apart,” she said. “All we can say for certain is that we have these bumper years and these zero years, and they are hard to predict.”

The Southern Nevada Health District has been conducting mosquito surveillance in the region since 2004. Its meticulous records show which mosquito species are present across the Las Vegas Valley year after year and where these flying insects have tested positive for diseases.

One of the most astonishing trends in the data was the explosive growth of Aedes aegypti mosquitoes, which were first identified in Las Vegas in 2017, said Vivek Raman, environmental health supervisor for the Southern Nevada Health District.

“In 2017, this mosquito was found in just a few ZIP codes,” said Raman, who oversees the health district’s mosquito surveillance program. “A few years later, it was six ZIP codes. Then 12 ZIP codes, then maybe 20, and now it’s in 48 different ZIP codes across the valley.”

In addition to being able to spread dengue, these insects are a major nuisance.

“Aedes aegypti are very aggressive daytime-biting mosquitoes,” Raman said. “They are just relentless biters.”

Unlike Culex mosquitoes, which prefer breeding near larger sources of water such as untended swimming pools, culverts or detention basins, Aedes aegypti tend to breed in much shallower standing water.

“One of the reasons they are spreading so quickly is the mosquito can lay its eggs in small containers, like if rain fills a child’s toy or tires or a wheelbarrow,” Raman said. “All it takes is a couple inches of water.”

Urban development in Las Vegas has also inadvertently spurred the spread of mosquitoes in the city. Golf courses, human-made lakes and other forms of artificial irrigation have all made this outpost in the Nevada desert a welcome home for mosquitoes, according to Messenger.

Climate change is likely also a factor, and it’s an active area of research for Messenger and other scientists. Warmer temperatures are expanding the range of geographies for mosquitoes around the world. A warmer atmosphere can also hold more moisture, which increases humidity and rain, both mosquito-friendly conditions.

In Las Vegas, how the interplay between local environmental factors and changing climate trends is affecting mosquito populations is less well understood, but the implications are paramount.

“Las Vegas is kind of a case study for what climate change is going to look like in other parts of the world,” Messenger said. “We’re seeing record-breaking temperatures, we’re becoming much more arid, precipitation is becoming much more aberrant and unpredictable. That’s what large parts of the world are going to look like over the next 15 to 25 years.”

What that means for mosquitoes in the city remains to be seen, but the problem so far shows no sign of slowing.

The Southern Nevada Health District conducts public outreach on how to identify and protect against mosquito breeding sites in and around homes, and how to prevent mosquito bites. But, controlling the number of mosquitoes in the city — and thus controlling the public health risk — will require a coordinated effort from the local government, Messenger said. Currently, there isn’t one in Las Vegas.

“You’ve got private pest companies that people can call for severe infestations, you have some work going on around wetlands, but what we don’t have, which many other jurisdictions have, is a centralized, coordinated abatement,” Messenger said.

That lack of coordination has resulted in mosquito populations building up resistance to insecticides, she added. A centralized effort could assess which chemicals are safe to use — particularly around humans — and monitor the performance of insecticides and pesticides to prevent mosquitoes from building up immunity.

In the years ahead, Messenger said, prevention and control will be key to protecting the residents of Las Vegas and its many visitors from around the world.

“The bottom line is that this is entirely preventable,” she said. “Nobody in southern Nevada, in Clark County, should be getting bit by mosquitoes and contracting any kind of virus.”

Zealousideal_Fig1305 on August 17th, 2025 at 23:15 UTC »

We've been dealing with this in SW Arizona as well. A couple years ago their population popped off, and now they appear during our monsoon season, or whenever it rains. Drought resilient eggs sounds like the best explanation.

The desert isn't as dry as people think, it's just that our rainfall is seasonal and very intense. A couple good storms will have the rivers running for weeks.

Back in 2021, we had an exceptional monsoon season, but all that water led to a huge uptick in mosquitos. It was terrible. And flies, so many fucking flies.

But the prior season (2020) was exceptipnally dry, one of the worst in recent memory. During that time, I think a lot of people got in the habit of leaving shit outside. So, all across the SW States, we collectively set the stage for rapid adaptation. Which led to a more climate resilient species of mosquito. (The only eggs that survived the 2020 drought were those with resilient traits, such as year long term egg viability and fast population regeneration.)

It feels like we're catching the first glimpse of the future to come.

*I should also mention the growth our cities saw from 2010-2020. Its still ongoing, but the sheer amount of people moving here means various foreign species were introduced (via eggs). And there was a huge uptick in people buying house plants in 2020.

The contributing factors are overwhelming. Even mundane viral trends can result a set of widely adopted practices/behaviors that lay a foundation for unpredictable enviromental backlash.

photog72 on August 17th, 2025 at 22:49 UTC »

Need to get the people who make Disney World in Florida, mosquito free. How the hell do they do that?

jackthemackattack on August 17th, 2025 at 22:22 UTC »

How can mosquitos even be that bad in Vegas? it's in the middle of a giant desert and every body of water has chlorine in it??