The Microscopic Burden of Climate Change: Increasing Risks of Dengue Virus in a Hotter World

BY CRISTINA GARCIA

Dengue, a viral illness transmitted by Aedes mosquitoes, remains one of the world’s most neglected tropical diseases (NTDs), despite its growing burden. The global incidence of dengue has spiked during the past few decades, with the World Health Organization documenting a tenfold rise in cases from 2000 to 2019.¹  In 2023 alone, more than five million cases were reported worldwide, resulting in over 5,000 dengue-related deaths across 80 countries and territories.²  Despite these alarming numbers, dengue continues to be overlooked in public health agendas, particularly in low- and middle-income countries, where limited resources and a general lack of attention hinder efforts to control its spread.³

The transmission of dengue occurs when an infected mosquito bites a human, transferring the virus into the bloodstream. Infected individuals typically experience fever, severe headaches, muscle and joint pain, nausea, rash, and pain behind the eyes. ⁴ While most cases are mild, severe forms can lead to hemorrhaging, organ failure, and even death — particularly in vulnerable populations, such as infants and the elderly. ⁴ Treatment options are relatively scarce, with no widely available vaccine for adults and only limited care to alleviate symptoms.² 

Once confined to tropical and subtropical regions, dengue now poses a growing threat to the United States. On June 25, 2024, the CDC issued a health advisory regarding the rising risk of dengue infections in the U.S., documenting that global cases in 2024 have been the highest on record. ⁵ As climate change accelerates the spread of Aedes mosquitoes into new areas, a proactive public health response is urgently needed in the US. 

How is climate change increasing the regional suitability of Dengue?

Aedes mosquitoes are highly sensitive to temperature and thrive in environments where the average daily temperature is between 25°C and 35°C, a range that is expanding due to global warming. ⁶  In addition, warmer temperatures accelerate the mosquito life cycle, shortening the egg development time and increasing reproductive rates.⁷  As a result, mosquito populations have also been growing faster in endemic regions, increasing the risk of dengue transmission.⁷ 

Higher temperatures also boost the replication of dengue viral particles within the mosquito, increasing the viral load in their saliva. ⁷ This higher viral load, in turn, raises the likelihood of virus transmission during bites.⁸  Further compounding these changes, rising temperatures accelerate the mosquito’s metabolic rate, increasing its energy demands. This has resulted in mosquitoes feeding more frequently, amplifying the risk of virus transmission. ⁹

In tandem with rising temperatures, increased rainfall, a direct result of climate change, creates more standing water where mosquitoes can lay their eggs.¹⁰ The combination of higher temperatures and more rainfall not only expedites mosquito population growth but also offers more breeding sites, especially in urban areas where dense human populations and artificial water reservoirs, such as drainage systems, provide abundant breeding grounds.¹⁰

Recently Recorded Cases in the United States

The increased levels of Dengue transmission, as a result of warming temperatures, is being recorded in the United States. In October 2023, the California Department of Public Health confirmed the state’s first case of locally acquired dengue—a Pasadena resident with no history of travel outside the United States. Since then, the number of cases has continued to climb . As of December 18, 2024, 16 locally acquired dengue infections were reported in California.¹⁰ Florida has also reported locally acquired dengue cases in multiple counties, with Miami-Dade experiencing the highest levels. As of December 7, 2024, Miami-Dade County had documented 44 locally acquired cases, contributing to 70 total cases across ten counties in Florida.¹¹ Most of these infections were identified as the more severe serotypes of  DENV-3 and DENV-4. ¹¹

Societal Implications

While the U.S. is only beginning to see the impacts of locally acquired dengue, the disease’s economic toll on affected countries is already well-documented. In Brazil, dengue fever costs the economy approximately $1 billion USD annually.¹²  When adjusted for under-reporting, the societal cost of dengue climbs to $1.2 billion USD. ¹³ These costs include not only direct medical care and vector control efforts, but also the considerable loss of human productivity. If the dengue outbreak trends seen in Florida and California continue to expand in the U.S., similar financial challenges could arise, with the potential for significant healthcare, prevention, and productivity-related expenses. ¹⁴ Healthcare systems would likely face similar strains as hospitals and clinics become overwhelmed with rising case numbers, requiring resources for patient care, surveillance, and prevention. ¹⁴ The costs of controlling the mosquito population, including insecticide spraying and public health campaigns, would further the burden, diverting resources from other critical health initiatives.

Dengue’s impact on the workforce is another important consideration. In Brazil, the disease has led to widespread absenteeism, particularly among working-age adults, which disrupts industries such as agriculture and construction  services. ¹⁵  A similar pattern in the U.S. could lead to a decline in productivity, especially in sectors that rely on hourly or seasonal labor. For example, workers in agriculture or construction who fall sick would miss work, resulting in direct economic losses for both employees and employers. The long-term impact could be more alarming if individuals experience lingering health effects, such as post-viral fatigue, which would further limit their ability to contribute to the workforce. ¹⁶

Beyond immediate illness, the societal consequences could also be experienced in schools and local economies. In Brazil, children often miss school during outbreaks, which not only disrupts their education but could also exacerbate existing educational inequalities. ¹⁷ In U.S. regions where outbreaks occur, students could face significant academic challenges, particularly in underfunded school districts that struggle to provide remote learning or make-up programs. Additionally, areas that rely on tourism and outdoor activities might see a decrease in the number of visitors due to public health concerns about dengue spread. ¹⁵

Potential and Promising Solutions 

As the threat of dengue grows, exacerbated by the effects of climate change, the need for action has never been more urgent. While it may seem straightforward, picking up trash plays a critical yet underestimated role in lowering the spread of dengue carried by mosquitoes.  For instance, the presence of standing water in discarded tires and containers along the Mexico-Texas border has been associated with increased mosquito breeding. ¹⁶  Furthermore, most-hurricane conditions in Florida often exacerbate mosquito breeding due to the accumulation of trash and spoiled food.¹⁷  As an example, power outages from hurricanes can cause food to spoil quickly, and when combined with standing water, create ideal breeding grounds for mosquitoes.¹⁷ Additionally, debris like fallen branches, leaves, and trash trap water, further expanding the habitat range of mosquitoes. Residents should thus remove both standing water and debris, especially after the storm. An additional practice that could be adopted is  Integrated Pest Management (IPM). This practice uses biological control agents, such as natural predators, as a form to control mosquito populations while minimizing the environmental impact.¹⁸  An example would be using mosquito-eating fish or applying larvicides to provide effective control while lowering the reliance on chemical pesticides. ¹⁸ With dengue continuing to spread, it is clear that fighting the disease not only necessitates traditional methods but also innovative solutions. 

With technology continuing to rapidly advance, the use of Artificial Intelligence (AI) along with machine learning to help with dengue control has garnered attention. Ningrum et al. focused on predicting dengue outbreaks in Dhaka, Bangladesh, by integrating environmental and climate data. The team used machine learning models to analyze factors such as temperature, rainfall, and humidity, to geospatially determine regions most prone to dengue cases. Models demonstrated an impressive 89.25% accuracy in predicting dengue outbreaks.¹⁹ Additionally, in a study by Riya, the team developed a diagnostic model utilizing a stacking ensemble classifier to detect dengue from complete blood count (CBC) reports. ²⁰ This method aimed to provide early detection through artificial intelligence, particularly in densely populated regions prone to outbreaks. In fact, the study achieved a 96.88% prediction accuracy of dengue cases.²⁰ This predictive ability allows health officials to respond proactively, allocating resources and deploying control measures before an outbreak occurs.

With the ability to diagnose dengue cases in ways never imaginable just a few years ago, AI brings a glimmer of hope to improved dengue case management.  Yet, this hope will slip through our fingers unless we act. The ultimate solution necessitates the political and societal will to make the active changes that will address the root causes of climate change. Simply adopting technology, no matter how advanced, is not enough for curtailing dengue cases. The fundamental causes of the crisis itself must be addressed. That is, the environmental shifts driven by climate change that are expanding the range of diseases and altering ecosystems. We must implement climate-conscious policies focused on reducing carbon emissions, and mitigating the impacts of extreme weather events in tandem with technological advancements to detect dengue cases. Only by taking action today can we protect not just our generation but also the health of generations to come.

Cristina Garcia is a first-year in Morse College.

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