Deadly Dengue Fever Rises as the US Cuts All Climate-Health Funding
Last week, the Centers for Disease Control and Prevention, or CDC, issued an urgent alert about dengue fever, a painful and sometimes deadly mosquito-borne illness common in tropical and subtropical parts of the world. Some 3,500 travelers from the United States contracted dengue abroad in 2024, according to the CDC, an 84 percent increase over 2023. “This trend is expected to continue,” the agency said, noting that Florida, California, and New York, in that order, are likely to see the biggest surges this year.
On Thursday, the United Kingdom Health Security Agency put out a similar warning, noting that there were 900 cases of travel-related dengue in the U.K. in 2024, almost 300 more infections than the preceding year. The two reports relayed a similar array of statistics about dengue, its symptoms, and rising caseloads. But the U.K. Health Security Agency included a crucial piece of information that the CDC omitted: It noted why cases are breaking records. “The rise is driven by climate change, rising temperatures, and flooding,” it said.
In the past, the CDC has readily acknowledged the role climate change plays in the transmission of dengue fever — but the political conditions that influence scientific research and federal public health communications in the U.S. have undergone seismic shifts in the months since President Donald Trump took office. The new administration has purged federal agency websites of mentions of equity and climate change and sought to dismantle the scientific infrastructure that agencies like the CDC use to understand and respond to a range of health risks — including those posed by global warming.
Last week, ProPublica reported that the National Institutes of Health, or NIH — the largest source of funding for medical research in the world — will shut down all future funding opportunities for climate and health research. It remains to be seen whether ongoing grants for research at this intersection will be allowed to continue. A few days later, U.S. Secretary of Health and Human Services Robert F. Kennedy Jr. announced his agency plans to cull 10,000 people from its workforce, including new cuts at CDC, an agency that was established in 1946 in order to prevent a different mosquito-borne illness, malaria, from spreading across the U.S.
Taken together, the suite of directives will prevent the U.S. and other nations whose scientists rely on NIH funding from preparing for and responding to dengue fever at the exact moment when climate change is causing cases of the disease to skyrocket. The abrupt subversion of the personnel and institutions tasked with responding to a threat like dengue bodes poorly for future health crises as climate change causes carriers of disease like mosquitoes, fungi, and ticks to expand their historical ranges and infiltrate new zones.
“The disease pressure in the last couple of years is very dramatic and it’s going in one direction — up,” said Scott O’Neill, founder of the World Mosquito Program, a nonprofit organization that infects mosquitoes with a naturally occurring bacteria to fight disease in 14 countries. For example, Brazil — the country that consistently registers the highest number of dengue cases — recorded a historic 10 million cases last year. The country reported 1.7 million cases in 2023.
The two types of mosquitoes that most often infect humans with dengue, Aedes aegypti and Aedes albopictus, thrive in the warm, moist conditions made more prevalent by rising atmospheric temperatures caused by fossil fuel combustion. The vast majority of annual dengue cases are asymptomatic, but about 25 percent of people infected, depending on the population, develop symptoms like fever, headache, and joint pain. A small percentage of those cases result in severe sickness, hospitalization, and even death.
The number of severe dengue infections corresponds roughly to the size of the pool of people infected every year. In 2023, when there were 6 million total dengue infections, 6,000 people died. In 2024, a year when there were more than 13 million cases registered globally, over 8,000 people died.
There is no cure for dengue. Patients in wealthier countries generally fare better than patients in developing regions with limited access to medical interventions like blood transfusions and places where waves of dengue patients overwhelm already-strained healthcare systems. Two dengue vaccines are available in some countries, but both have serious limitations in terms of efficacy and how long they confer immunity.
The NIH began taking climate change and health research seriously in 2021, and the institutes have funded dozens of studies that probe every aspect of the climate-dengue connection since. NIH-funded researchers have sought to understand how warmer temperatures shift the geographic ranges of Aedes mosquitoes, which factors predict dengue outbreaks, and how communities can protect themselves from dengue following extreme weather events.
These studies have taken place in the southeastern U.S., where dengue is becoming more prevalent, and internationally, in countries like Peru and Brazil, where dengue is a near-constant threat. The NIH has also funded studies that bring the world closer to finding medical and technological interventions: more effective vaccines and genetically engineered mosquitoes that can’t develop dengue, among other solutions.
“Disease doesn’t have national borders,” said an American vector biologist who has received funding from the NIH in the past. She asked not to have her name or affiliated academic institution mentioned in this story out of fear of reprisal from the Trump administration. “I’m worried that if we’re not studying it, we’re just going to watch it continue to happen and we won’t be prepared.”
Americans aren’t just bringing cases of dengue fever home with them from trips abroad; the disease is also spreading locally with more intensity in warmer regions of the country and its territories. Last March, Puerto Rico declared a public health emergency amid an explosion of cases on the island. By the end of 2024, Puerto Rico registered over 6,000 cases — passing the threshold at which an outbreak officially becomes an epidemic. More than half of the known infections led to hospitalization. Close to 1,000 cases have been reported there so far this year, a 113 percent increase over the same period in 2024. California and Florida reported 18 and 91 locally-acquired cases of dengue, respectively, last year. California registered its first-ever locally-acquired case of dengue in 2023.
“Dengue is already found in many places in the U.S. that have never seen this disease before,” said Renzo Guinto, a physician and head of the Planetary Health Initiative at the Duke-NUS medical school in Singapore. “To combat this emerging climate-related health threat, U.S. scientists must collaborate with others working in dengue overseas. With no resources and capacity, how can such collaboration occur?”
There are limited non-government sources of funding for climate and health research. The money that is available to American researchers is primarily offered by private foundations like the Gates Foundation and the Wellcome Trust. The grants these philanthropies offer annually pale in comparison to the $40 million Congress made available annually through the NIH for climate and health research in the two years before Trump took office. Researchers will be forced to compete for a small pool of funding in the coming years, which will likely lead to fewer studies and less innovation in the years to come. “The end result will be that much less of this work would be done — we would all tell you to the detriment of Americans long term,” said the vector biologist.
As dengue spreads with more intensity in the countries where it is already common and slips across borders into zones like North America where the disease is still comparatively rare, it’s clear countries need to expand their arsenals of disease-fighting weapons. But the U.S. appears to be leading a charge in the opposite direction, with thousands of lives at stake.
“We’re at a time when we need acceleration of innovation and solutions to very pressing global problems,” said O’Neill, whose organization receives funding from governments around the world, including the U.S. “It’s not the time to let ideology drive science rather than let science drive itself.”
This article originally appeared in Grist.
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