In the shimmering heat of the Las Vegas Valley, a quiet but relentless threat is on the rise. Mosquitoes, once primarily a seasonal nuisance, have flourished in unprecedented numbers across southern Nevada, fueled by a confluence of factors that experts warn could spell trouble not just for the region, but for much of the world. According to the Gazette Review, insecticide resistance, climate change, and rapid urban development have converged to create ideal breeding grounds for these persistent pests.
Clark County’s mosquito population is now dominated by two species: Aedes aegypti, notorious for spreading dengue and chikungunya, and Culex mosquitoes, which transmit West Nile virus. Scientists have recently sounded the alarm about mosquitoes’ growing resistance to insecticides, a development that leaves public health officials scrambling for new solutions. Louisa Messenger, assistant professor in environmental and global health at the University of Nevada, didn’t mince words when she described the situation as “a ticking time bomb.”
Messenger’s warning is not without cause. Las Vegas, a city that attracts more than 48 million visitors annually, is uniquely vulnerable to mosquito-borne illnesses. As Messenger explained, it would take only a handful of infected mosquito bites to ignite local transmission of diseases like West Nile virus and dengue fever. The threat is not hypothetical: in 2024, Las Vegas recorded 26 human cases of West Nile virus. Testing that year revealed that most mosquitoes in the area harbored the virus, making the risk of exposure alarmingly high. While no human cases have been confirmed so far in 2025, mosquitoes in several neighborhoods have already tested positive for the virus, suggesting the danger is far from over.
Since 2004, the Southern Nevada Health District has kept a close eye on mosquito activity, tracking both species and the spread of disease. The picture has grown more concerning over time. In 2017, mosquitoes were found in just a handful of ZIP codes. By 2025, they had established themselves in 48 ZIP codes across the Las Vegas Valley. The expansion is due in no small part to the adaptability of Aedes aegypti, which prefer shallow, standing water. Urban features such as artificial lakes, golf courses, and even backyard water features have inadvertently provided mosquitoes with countless new breeding sites.
Climate change is amplifying the problem. Rising temperatures, increased rainfall, and higher humidity levels have created an environment in which mosquitoes thrive. Messenger and other experts point out that these conditions are not unique to Nevada; they are part of a global trend that is reshaping the reach of mosquito-borne diseases.
Indeed, the threat posed by mosquitoes extends far beyond Las Vegas. According to The New York Times, a mosquito-borne virus that can leave victims debilitated for years—chikungunya—is spreading to new regions as climate change creates ever more hospitable habitats for the insects. So far in 2025, more than 240,000 cases of chikungunya have been reported worldwide, with 200,000 in Latin America and 8,000 in China. In response, Chinese authorities have launched urgent public health measures reminiscent of those used during the Covid-19 pandemic.
Chikungunya, like dengue and Zika, is transmitted by Aedes aegypti and Aedes albopictus mosquitoes. The disease is rarely fatal, but it can cause excruciating joint pain and weakness that lingers for months or even years. “You have people who were working, with no disabilities, and from one day to the next, they cannot even type on a phone, they can’t hold a pen, a woman cannot even hold a knife to be able to cook for her family,” said Dr. Diana Rojas Alvarez, who leads chikungunya work at the World Health Organization (WHO). She emphasized that the virus “really impacts quality of life and also the economy of the country.”
Chikungunya is not currently circulating in the United States or Canada, but cases have been documented in France, Italy, and Mexico. By the end of 2024, transmission had been reported in 199 countries on every continent except Antarctica. The WHO warns that current patterns resemble a global outbreak from two decades ago, which infected half a million people and left a legacy of disability in its wake.
The economic and social toll of chikungunya is significant. Up to 40 percent of those infected suffer from chronic joint pain, a figure that dwarfs the long-term impact of many other infectious diseases. During a major outbreak in India between 2005 and 2007, chikungunya was responsible for more than two-thirds of all reported disabilities, outpacing conditions like cancer, arthritis, and diabetes.
Climate change is accelerating the spread of chikungunya-carrying mosquitoes in several ways. Warmer, wetter weather provides more breeding sites, while extreme weather events—from floods to droughts—can force populations to cluster in areas with poor sanitation and water management, further increasing risk. In recent years, Aedes albopictus has expanded its range across Europe, reaching cities like Amsterdam and Geneva. In South America, Aedes aegypti thrives in rapidly growing urban centers with unreliable water systems, often in low-income neighborhoods.
Scott Weaver, scientific director of the Galveston National Laboratory in Texas, offered a sobering assessment: “Fatality levels are low, but we really care about chikungunya because it leaves people with months or potentially years of debilitating pain. That has not only an individual toll but also a social one, with strain on health care systems, economic impact, the demand on caregivers, a lot of things.”
Despite the scale of the threat, options for prevention remain limited. Two vaccines for chikungunya exist, but they are produced in small quantities and are prohibitively expensive for most countries. The newest vaccine, developed by Bavarian Nordic, costs about $270 per shot in the United States. Efforts are underway in Brazil to develop a more affordable version, but neither vaccine has yet received the kind of WHO recommendation that would spur widespread use. Conducting large-scale clinical trials is challenging, as outbreaks often subside before research can begin.
With vaccines out of reach for most, the best defense against chikungunya—and other mosquito-borne illnesses—remains basic: avoid getting bitten and reduce mosquito breeding sites. In China, public health teams are going door to door, searching for stagnant water. Surveillance of chikungunya is still weak globally, a situation made worse by recent cuts in U.S. funding that had supported disease tracking in low-income countries. Dr. Rojas noted that the WHO is working to improve surveillance and to determine how much of the current surge in cases is due to new transmission versus better reporting.
Chikungunya is not a new threat. First identified in Tanzania in the 1950s, it caused sporadic outbreaks in Africa and Asia for decades before exploding onto the global stage in 2004. That year, an outbreak in Kenya spread to La Réunion, a French territory in the Indian Ocean, infecting a third of the island’s population. The virus then moved to South Asia, the Caribbean, and eventually the Americas, where it continues to circulate alongside dengue and other mosquito-borne illnesses. Since 2023, cases in South America have climbed steadily.
The story of mosquitoes in Las Vegas and the global march of diseases like chikungunya is a stark reminder of the interconnectedness of climate, urban development, and public health. As mosquitoes adapt and thrive in our changing world, the need for vigilance—and innovation—has never been greater.