A recent post at USA Today, “Dengue fever spiked to record levels in 2024: Climate change will make it even worse,” claims that global warming has already led to a spike in dengue fever, and will lead to further increases of the disease as warming continues. This claim is likely false. No data supports the claim, rather the climate change impact on Dengue fever, as with other vector-borne diseases, is in the realm of theory, relying heavily on counterfactual computer modelling.
USA Today reports that there has been an increase in the number of infections from dengue fever, “three times the number of cases in 2023, which was record-setting at the time.” The report relies heavily on a study published in medRxiv “Climate warming is expanding dengue burden in the Americas and Asia,” which claims to have found that climate change caused the vector-borne illness’ spread as temperatures have risen. This study can be categorized as largely an attribution study with a little real medical data thrown in. However, like all climate attribution studies, it presumes that climate change would have an impact on the spread of dengue and other vector-borne illnesses, and relies on the sixth generation climate models (CMIP6) that are known to be flawed because they run too hot.
The study authors admit that their method is an expansion of the kind of work done by other attribution groups, “it is among the first studies to attribute changes in infectious disease to climate change—expanding on the attribution literature centered on more direct effects such as heat waves, storms, and fires—providing a road map for future studies on other ecological and health impacts.” This is notable, because those other attribution studies are deeply flawed and do not reflect reality, as Climate Realism has repeatedly shown.
The study acknowledges that many factors outside of temperature also influence the prevalence of mosquito-driven diseases like dengue, and although they claim that they worked to isolate and control for or rule out those other factors effects, it is unclear whether they were able to successfully do so. One would think that if rising global average or regional temperatures were causing spikes in dengue in Southeast Asia and Central and South America, as the study indicates, that the United States would see it as well. However, the USA Today article admits that the U.S. “hasn’t had a high rate of infections compared with the early 2010s.”
As importantly, the countries covered are largely equatorial, where temperatures, as opposed to at the poles, haven’t changed that much. Dengue was native to and already endemic in those tropical and subtropical regions. Humidity hasn’t increased there, and there is no reason to believe the environment is more conducive to mosquitos flourishing in those countries now than before. It is likely that the reported increase in Dengue fever is just that, a reported increase, with better detection and tracking of the disease available now in those regions than has existed previously.
One individual interviewed by USA Today later in the article, Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, admits that global warming “isn’t the only factor that explains the continued rise in dengue.” He went on to explain that impoverished communities “often lack air conditioning and window or door screens […] also lack efficient sanitation to remove standing water where mosquitoes can grow and infect people nearby.”
These are by and large the factors that have the greatest influence on whether or not a vector borne illness, like Dengue Fever, can spread, along with lack of widespread access to and use of modern pesticides, as discussed in detail in “Stop Misinforming about Malaria’s Spread, Washington Post.” Urbanization, for example, can affect the spread of mosquitos through management of standing water, as discussed by Climate Realism using Houston as an example, here. A chapter in Climate Change Reconsidered II: Fossil Fuels, discusses how the results of more than a dozen peer-reviewed studies show that temperature alone is not enough to guarantee the greater incidence of mosquito-spread illnesses, and one expert from the Centers for Disease Control and Prevention even called attribution like that promoted by USA Today “facile.”
Ironically, USA Today ends their article by explaining that all you need do to prevent the spread of dengue is protect yourself from getting bit by mosquitos using technology like “loose-fitting clothing” and “insect repellant.” These are much more direct and affordable strategies than cutting fossil fuel use to reduce greenhouse gas emissions in the hopes of reducing temperatures slightly, a very indirect approach to mosquito borne disease reduction.
