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Increasing temperatures worldwide are altering the realm of human wellness. For instance: The occurrence of dengue fever might surge by up to 76% by 2050 due to climate change affecting a significant portion of Asia and the Americas, as per a recent investigation led by Marissa Childs, a scholar at the University of Washington.

Dengue fever, a disease transmitted by mosquitoes once primarily limited to tropical regions, frequently manifests flu-like symptoms. In the absence of appropriate medical attention, it has the potential to progress to severe hemorrhaging, organ failure, and even fatalities. 

The research, published on Sept. 9 in PNAS, represents the most thorough estimation to date regarding how temperature changes influence the spread of dengue. It offers the first concrete evidence that a warming climate has already heightened the disease’s impact.

“The repercussions of temperature were significantly greater than I anticipated,” stated Childs, a UW assistant professor of environmental health who carried out a considerable portion of the research during her doctoral studies at Stanford University. “Even minor temperature variations can substantially affect dengue transmission, and we are already witnessing the signs of climate warming.”

The analysis scrutinized over 1.4 million records of local dengue occurrence across 21 nations in Central and South America, as well as Southeast and South Asia, capturing both epidemic peaks and background infection levels.

Dengue flourishes in a “Goldilocks zone” of temperatures — with incidence peaking at roughly 27.8 degrees Celsius, or 82 degrees Fahrenheit, sharply rising as cooler areas warm but slightly decreasing when already hot locales exceed the ideal range. Consequently, some of the most significant increases are expected in cooler, densely populated regions of countries such as Mexico, Peru, and Brazil. Numerous other endemic areas will continue to bear a heavier burden of dengue fueled by warming. Conversely, a few of the hottest lowland regions might see slight reductions.

Nonetheless, the overall global effect is a steep increase in the disease.

The results indicate that heightened temperatures due to climate change were accountable for an average 18% rise in dengue incidence across 21 countries in Asia and the Americas from 1995 to 2014 — which translates to over 4.6 million additional infections each year, based on current incidence estimates. Cases could rise another 49% to 76% by 2050, depending on greenhouse gas emission levels, according to the research. At the higher end of the predictions, dengue incidence could more than double in several cooler areas, including regions in the study countries that already house over 260 million individuals.

“Numerous investigations have associated temperature with dengue transmission,” remarked senior author Erin Mordecai, a biology professor at the Stanford School of Humanities and Sciences. “What differentiates this study is that we can isolate warming from other factors influencing dengue — such as mobility, land use changes, and population dynamics — to determine its effect on the actual dengue burden. This isn’t merely hypothetical future change; it’s a considerable amount of human suffering that has already transpired due to warming-induced dengue transmission.”

The researchers warned that their estimations are likely conservative. They do not consider regions where dengue transmission is irregular or inadequately reported, nor do they account for sizable endemic areas like India or Africa where comprehensive data is unavailable or not publicly accessible. Additionally, the researchers emphasized recent locally transmitted cases in California, Texas, Hawaii, Florida, and Europe — indicating the expanding reach of dengue. Urbanization, human migration, and viral evolution could heighten risks, while medical advancements may help mitigate them, rendering projections uncertain.

Proactive climate mitigation would significantly reduce the dengue disease burden, according to the research. Simultaneously, adaptation will be crucial. This encompasses improved mosquito control, bolstered health systems, and the potential extensive deployment of new dengue vaccines.

In the interim, the findings could assist in directing public health strategies and reinforcing efforts to hold governments and fossil fuel corporations accountable for climate change impacts. Attribution studies are increasingly entering legal proceedings and policy discussions, utilized to assign liability for climate damages and to facilitate funds for countries most severely impacted.

“Climate change is not solely altering weather patterns — it has cascading effects on human health, including exacerbating disease transmission via mosquitoes,” Mordecai stated. “Even as the U.S. federal government reduces investments in climate mitigation and health and climate research, this work is more vital than ever for anticipating and alleviating the human suffering caused by fossil fuel emissions.”

The co-authors of the study include Kelsey Lyberger of Arizona State University, Mallory Harris of the University of Maryland, and Marshall Burke of Stanford. Lyberger and Harris carried out much of their work while at Stanford.

The investigation was funded by the Illich-Sadowsky Fellowship through the Interdisciplinary Graduate Fellowship program at Stanford University; an Environmental Fellowship at the Harvard University Center for the Environment; the National Institutes of Health; the National Science Foundation (with the Fogarty International Center); the Stanford Center for Innovation in Global Health; the Stanford King Center on Global Development; and the Stanford Woods Institute for the Environment.

Adapted from a press release by Stanford University. For further details or to reach the researchers, contact Alden Woods at [email protected].

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