When the chills, body shivers, and pounding headache first hijacked my system, I was 30,000 feet above the Pacific Ocean, midway through a 14-hour flight to Manila in the Philippines. My home in Baja California Sur, Mexico, was some 5,000 miles behind me. And I had no clue which pathogen had stowed itself away in my bloodstream before my departure.
Four days later – following many visits to pharmacies and a small island clinic – a volley of blood tests finally revealed what was wrecking my body: dengue fever, also known as breakbone fever.
Fittingly for the disease’s common name, it was the sharp and nearly-paralyzing body aches in my ankles, calves, and even between my fingers that prompted my Filipino medical team to test for dengue.
The virus has a long history in the Philippines and Mexico alike. But dengue had hardly crossed my mind while I was living the past year in the arid, subtropical desert of Baja California Sur, Mexico. Still, just before my infection in September 2025, a series of tropical storms had soaked the landscape, turning it green and ripe for mosquito propagation.
On day seven after my symptoms began, I was hospitalized as my blood platelet count dropped dangerously low.
The fingerprints of climate change
Dengue fever now ranks as the world’s fastest-growing and one of the most common mosquito-borne diseases. Case counts have accelerated in parts of Mexico, Latin America, and Southeast Asia in recent years – fueled by globalization and climate change, according to multiple recent studies.
Climate research now forecasts a significant rise in dengue exposure and transmissions by midcentury as global temperatures increase, plaguing places where it already circulates as well as cooler regions where significant outbreaks have been less common historically.
“Climate change allows mosquitoes to move to places where they previously could not survive,” said Jose Ramos-Castañeda, a dengue expert with Mexico’s Center for Research on Infectious Diseases in Cuernavaca, Mexico, in Spanish.
The mosquitoes spreading dengue
The culprits behind the spread of the virus are the common Aedes aegypti mosquito and, in some places, the Aedes albopictus mosquito.
Both species transmit it to humans via discrete bites to the skin. Although a dengue patient can’t directly infect someone else, mosquitoes spread dengue when they bite one infected person and then move on to another victim.
Both species prefer urban settings and bite during daylight hours. They also transmit yellow fever, Zika, and chikungunya viruses.
The females feed on human and animal blood for protein to sustain egg production (males don’t bite). They lay their eggs in still water, often preferring small containers like tires or debris. And one individual mosquito can live up to eight weeks, feeding on many humans in that life span.
Globally, mosquitoes cause more than 700,000 deaths per year, making them the world’s deadliest animals. And our planet, in some ways, is becoming more hospitable to them.
How warming is fostering dengue
The shift toward a world with more dengue is already well underway.
In 2024, the approximately 14 million recorded cases of dengue fever set a global record, more than double the record of around seven million set the previous year, according to a 2025 study in the International Journal of Infectious Diseases.
Many cases go unreported, so experts estimate that the true number ranges between 100 million and 400 million annually.
A fall 2025 analysis published in Proceedings of the National Academy of Sciences presented the most comprehensive estimate yet of how temperature shifts affect dengue’s spread.
The research shows that higher temperatures from climate change contributed to an average 18% of dengue cases across 21 countries in Asia and the Americas from 1995 to 2014. This translates to millions of new infections each year.
Paired with future climate models, their work also showed that dengue cases are likely to climb between 49% and 76% globally over the next 35 years, depending on how much heat-trapping pollution we add to the atmosphere.
For Mexico, a median climate change scenario would result in a 147% surge of dengue in the state of Jalisco, home to Mexico’s second-most populous city, Guadalajara. Similar spikes are predicted for the states of Chihuahua and Baja California, while the state of Mexico in the center of the country would see a 267% jump.
One important pattern that emerged across multiple countries and continents: Higher-elevation and farther-from-the-equator regions where dengue cases already occur occasionally will start to see a significant uptick in transmission.
“Places on the cooler end really popped out,” said Kelsey Lyberger, a quantitative ecologist at Arizona State University and the co-author of the study.
Stacking climate variables and transmission
In Mexico’s northwestern state of Baja California Sur, a dengue outbreak in 2013-2014 caused a 650% spike in recorded infections for the region.
With more than 8,000 reported cases, it was a stunning epidemic for the driest state in Mexico, where historic rainfall averages less than seven inches (176 millimeters) per year.
Although scientific data is lacking and conflicting on the exact relationship between rainfall and dengue trends, local health advisories and community warnings in Mexico and other countries often follow hurricanes and tropical storms that bring seasonal rainfall.
Annual outbreaks in Baja California Sur also occurred in 2023 and 2024, particularly affecting the population centers of Los Cabos and La Paz, where I spent most of my time just before my infection.
Experts say they know that shifting rainfall patterns, tropical storms, hurricanes, and flooding influence mosquito activity and dengue transmission. But for those factors, it’s difficult to pin down the exact role of the changing climate.
Lyberger points to examples of the complex ways that storms can influence dengue transmission: More frequent and more damaging hurricanes can destroy window screens, enabling mosquitoes to slip inside. Storms can also destroy homes, leaving displaced people vulnerable to bites.
In addition to climate variables, the exponential growth of global trade and travel in recent decades is also transporting mosquito eggs and dengue-infected people across borders at a higher rate than ever.
Tires, for example, make prime habitat for Aedes aegypti eggs, which can lie dormant for months during shipment and transport. Similarly, I became a possible international dengue vector when I traveled from Mexico to the Philippines and got bitten by local mosquitoes.
This global transit matters because there are four subtypes of the dengue virus (dengue-1, dengue-2, dengue-3, and dengue-4).
Although a person typically gains lifelong immunity to a dengue subtype after first infection, they remain vulnerable to the other three strains. And second or third dengue infections for an individual can be more dangerous than the first, increasing the chances of life-threatening hemorrhagic dengue, characterized by plasma leakage and bleeding. Globalization seems to be exposing people to additional subtypes more frequently.
“There are probably some places still with a single serotype, but this is becoming much more rare with globalization, transport, and people traveling,” Lyberger says.
Today, all four serotypes are present in Mexico.
The bacteria that fight dengue inside a mosquito’s body
One community defense for dengue fever that is growing globally sounds counterintuitive: the release of millions of new mosquitoes into a region where dengue is spreading. But these aren’t just any mosquitoes.
The released mosquitoes are males infected with a naturally occurring insect bacterium called Wolbachia. When these introduced mosquitoes breed with wild Aedes aegypti females, they pass on Wolbachia, which reduces dengue transmission to humans by making it more difficult for the virus to reproduce inside the mosquito, according to the World Mosquito Program that launched the Wolbachia method in 2011.
This year alone, Mexico has released tens of millions of Wolbachia mosquitoes into targeted areas where dengue outbreaks have occurred.
Many of these communities also fumigate city streets, filling the air with a fog of insecticide targeted to kill adult mosquitoes. Health agencies also encourage the public to apply bug spray liberally.
Lyberger says the “tip and toss” standing water method is effective for anyone trying to rid dangerous mosquitoes or eggs from their home or property. It involves identifying and removing standing water from containers, surfaces, and other potential spawning spots for Aedes aegypti.
Medical treatment of the virus
On the medical side, no particular medication is approved for dengue. Multiple antiviral meds are in trial phases and showing promising results for treating the infection.
Vaccines have also surfaced, including Dengvaxia, which was approved in Mexico and some other countries in 2015. But medical risks and limited accessibility hampered the distribution and effectiveness, prompting the manufacturer of Dengvaxia to cease production last year.
Ramos-Castañeda said a more viable pharmaceutical strategy could be a game changer in the years ahead.
“I don’t think [dengue] will be a catastrophic issue long term,” he said. “I believe that the vaccine will be a determining factor in the control of dengue in the future.”
A long recovery
At the hospital where I was treated for dengue, round-the-clock IV fluids and some improved blood numbers after two nights earned me a discharge with a regimen of basic meds, supplements, and a strict diet.
My full recovery took more than six weeks – particularly my liver function, as my enzyme levels shot 2,000% above the normal range. Doctors recommended vitamins, hydration, rest, and dietary restrictions like avoiding alcohol.
By the time my final blood test came back normal, I was back home in Baja California Sur and fielding weekly texts from one friend after the next who told me they had come down with dengue.
For one friend, it was the third infection since her youth. She did not know the second or third infection might pose more danger than the first.
Another friend who was pregnant was infected, presenting particular risks to her fetus.
The best I could offer was a healthy meal drop-off, a hug, and a roundup of doctor’s advice I gleaned from my immersive experience: avoid aspirin, which can thin the blood and worsen dengue symptoms; seek multiple complete blood count tests to know what’s happening in your system (especially blood platelet levels); and test liver function, which can nosedive more than a week or two after symptoms begin.
Spreading this general knowledge might be a key, practical step to weathering our likely future with heightened dengue exposure.
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Great Job Tree Meinch & the Team @ Yale Climate Connections Source link for sharing this story.
