Relationship Between Climate Change on Vector-Borne Diseases

Dr. Emily Johnson^1*, Prof. Carlos Mendes¹, Dr. Fatima El-Sayed¹

¹ Department of Environmental and Public Health, University of Nairobi, Nairobi, Kenya

* Corresponding Author: email: [email protected]

Abstract

Climate change exerts profound effects on human health, with vector-borne diseases (VBDs) representing one of the most pressing concerns. Illnesses such as malaria, dengue, and yellow fever—transmitted through vectors including mosquitoes, ticks, and flies—are particularly sensitive to environmental variations. Shifts in temperature, rainfall, and humidity directly alter the habitats, behaviors, and population dynamics of these vectors, thereby reshaping patterns of disease transmission. This article reviews the relationship between climate change and VBDs from a public health standpoint. It examines not only climatic drivers but also human-mediated factors—such as migration, rapid urban growth, and land-use modifications—that facilitate disease spread. The discussion emphasizes the importance of adopting integrated strategies to reduce climate-related risks, including vector control tools like insecticide-treated nets and indoor residual spraying, alongside broader public health measures such as vaccination programs and robust surveillance systems. Ultimately, climate change presents substantial challenges to global health, particularly in low-resource settings with fragile infrastructure. The paper underscores the urgency of proactive measures to mitigate these threats and safeguard populations against the growing burden of VBDs.

Keywords: Climate change, vector-borne diseases, Public health, Malaria, dengue fever, Yellow fever

 

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1. INTRODUCTION

The Earth absorbs incoming shortwave radiation from the sun, of which roughly one-third is reflected back into space. The remaining portion is taken up by the land, oceans, atmosphere, and living organisms. Under normal circumstances, the energy absorbed from the sun is balanced by the radiation emitted back into the atmosphere and space. This re-radiation occurs primarily in the form of longwave infrared energy. However, this equilibrium between incoming and outgoing radiation can be disrupted by several factors, including fluctuations in solar output, gradual variations in the Earth’s orbital path, and the intensification of the greenhouse effect (Santra, 2016; WWF, 2017). Greenhouse gases such as carbon dioxide, methane, nitrous oxide, water vapor, and ozone—present in both the stratosphere and troposphere—trap heat near the Earth’s surface, thereby driving a warming effect. This phenomenon arises because the atmosphere allows incoming solar radiation to pass through but absorbs much of the outgoing thermal energy emitted from the Earth’s surface. While the greenhouse effect is a natural process essential for maintaining habitable temperatures, human activities since the onset of industrialization have amplified it significantly, resulting in what is termed the “enhanced greenhouse effect” (Santra, 2016). Weather and climate are intrinsically linked to atmospheric processes. The atmosphere, a gaseous envelope extending about 966 km above sea level, is composed of nitrogen (78%), oxygen (21%), carbon dioxide (0.003%), and trace amounts of helium, argon, other rare gases, and approximately 4% water vapor by volume. The lower region of the atmosphere, the troposphere, extends from the Earth’s surface to around 10 km and is the primary zone where weather occurs. Within this layer, temperature generally decreases with increasing altitude. The troposphere also contains dust, microorganisms, and gases released from fossil fuel combustion, all of which influence weather and climate variability across regions. Key elements shaping climate include temperature, precipitation, winds, and pressure, while broader climatic factors encompass latitude, ocean currents, vegetation, topography, and continental positioning.

 

2. GREENHOUSE GASES ELICIT CLIMATE CHANGE

Greenhouse gases (GHGs) represent a unique category of atmospheric constituents that possess the ability to trap radiation which would otherwise escape into outer space. By doing so, these gases create a warming effect within the Earth’s atmosphere. Their role can be compared to that of a physical greenhouse, which allows sunlight to pass through while preventing the escape of heat, thereby ensuring that plants inside remain warm. This natural greenhouse phenomenon is vital for sustaining life, since without it, the global average temperature would be around –18°C, an extreme level of cold that would render the Earth uninhabitable. Thanks to the action of GHGs, the actual average surface temperature of the Earth is maintained at approximately 15°C. The major greenhouse gases include carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and others such as water vapor and ozone (Michigan State University Extension, 2011). Human-induced activities, particularly the rapid and excessive burning of fossil fuels, have been identified as primary drivers of the rising levels of carbon dioxide in the atmosphere. This increase is further compounded by the depletion of natural carbon sinks, such as forests and oceans, which normally absorb and store carbon. Together, these processes disrupt the balance of carbon in the Earth system, contributing directly to an unprecedented rise in global temperature (Sheffran, 2008). Empirical measurements and longitudinal studies further reveal that human actions are responsible for escalating the atmospheric concentration of not only CO₂, but also nitrous oxide, hydrofluorocarbons, and chlorofluorocarbons—gases that have high global warming potential and long atmospheric lifespans (Sarkingobir et al., 2021). While greenhouse gases exist naturally and are essential for maintaining a habitable climate, it is their sharp increase due to anthropogenic sources that transforms them from a protective mechanism into a major threat to environmental and human well-being. This excessive buildup of GHGs leads to an intensified warming effect on the Earth’s surface and serves as one of the principal causes of contemporary climate change (WHO, 2003; WHO, 2009).

When solar energy reaches the Earth’s atmosphere, it undergoes multiple interactions. Approximately 30% of the incoming solar radiation is reflected back into space by clouds, aerosols, and the Earth’s surface. About 20% is absorbed by atmospheric constituents such as water vapor, suspended particles, and cloud cover. The remaining 50% is absorbed directly by the Earth’s surface, including land masses and oceans. For the system to remain stable, the energy absorbed must be released back into space in the form of outgoing radiation. This outgoing energy primarily manifests as longwave infrared radiation. Because the Earth’s atmosphere is relatively transparent to incoming shortwave solar radiation but comparatively opaque to outgoing infrared radiation, it traps a significant portion of the heat. This re-radiated energy warms the atmosphere and surface, resulting in what is formally described as the natural greenhouse effect (MacCracken, 2001). However, with the onset of industrialization and the intensification of human activities in the 20th and 21st centuries, the natural greenhouse effect has been amplified into what is now recognized as the enhanced greenhouse effect. This process is primarily fueled by anthropogenic emissions of carbon dioxide, methane, nitrous oxide, and water vapor. For instance, fossil fuel combustion, industrial production, and large-scale transportation release massive amounts of CO₂ into the atmosphere. In addition, land-use changes such as deforestation eliminate major carbon sinks, thereby reducing the Earth’s ability to naturally absorb carbon from the atmosphere. These processes that release carbon into the atmosphere are referred to as carbon sources, while those that absorb and offset carbon—such as forests, soil systems, and oceans—are termed carbon sinks (United States Environmental Agency, 2017; University of Victoria, 2020). Oceans, for example, act as significant carbon sinks through the process of dissolving atmospheric CO₂, while terrestrial ecosystems store carbon via photosynthesis and reduced respiration (Michigan State University Extension, 2011).

Ultimately, the distinction between natural and enhanced greenhouse effects lies in scale and causation: while the natural greenhouse effect provides a stable, life-sustaining climate, the enhanced greenhouse effect—driven by human-induced emissions—has disrupted this balance, generating global warming and fueling climate change. The health of the planet is largely assessed through its carbon status and the dynamics of the carbon cycle, which involves the continuous exchange of carbon among the atmosphere, land, and oceans. For ecological stability, a balance must exist between the volume of carbon released and the amount stored. However, anthropogenic activities have increasingly disrupted this balance, creating conditions that are harmful for both ecosystems and human societies (Lu et al., 2022). A carbon source refers to any process or activity that releases more carbon dioxide into the atmosphere than it absorbs. Natural carbon sources include volcanic eruptions, wildfires, decomposition of organic matter, respiration, digestion in animals, and emissions from freshwater bodies and oceans. In addition to these natural contributors, human activities such as fossil fuel extraction, mining, large-scale deforestation, and industrial operations have become major carbon sources. On the other hand, a carbon sink represents any system or process that absorbs and stores more carbon dioxide than it releases. Natural carbon sinks include oceans, lakes, forests, vegetation, carbonate rocks, and fossil fuels buried in geological formations (Santra, 2016; Liu et al., 2022). Together, the interaction of carbon sources and sinks determines the atmospheric carbon balance, which directly influences climate regulation.

 

3. SOME IMPACTS OF CLIMATE CHANGE

 

The continuous increase of greenhouse gases in the atmosphere is the driving force of global climate change. This process triggers a wide range of environmental, social, and health-related consequences.

Sea-level rise – Global warming leads to sea-level rise primarily through four mechanisms: (i) thermal expansion of seawater as it warms, (ii) accelerated melting of mountain glaciers, (iii) large-scale melting of the Greenland ice sheet, and (iv) the collapse or melting of the Antarctic ice sheet (Santra, 2016; Morisetti & Brown, 2021). The cumulative effect of these processes threatens coastal ecosystems and human settlements.

Changes in crop yield – Agricultural productivity is directly influenced by climatic shifts. Elevated carbon dioxide concentrations may increase crop yields in some areas, in certain cases by 60–80%, as CO₂ can be converted into plant sugars. For example, C3 crops such as wheat, rice, soybeans, and barley have shown experimental yield increases of up to 30%. However, these potential gains are often offset by adverse climate-related factors, including pest proliferation, pathogen outbreaks, and ecosystem stress caused by climate variability (MacCracken, 2001; Kaddo, 2016).

Water balance – The greenhouse effect also disrupts hydrological cycles. Regions already experiencing high temperatures are projected to suffer more frequent and severe water crises, while other regions may face excessive water availability, potentially leading to floods and waterlogging (Kaddo, 2016).

Human health – Climate change exerts profound effects on public health. Rising temperatures increase heat-related illnesses and mortality, while extreme weather events disrupt livelihoods and healthcare infrastructure. In addition, climate change exacerbates air pollution, drought-related malnutrition, mental health challenges, and the spread of both food-borne and water-borne diseases. Particularly concerning is the expansion of vector habitats, which enhances the spread of infectious agents such as mosquitoes and ticks (Heirings, 2010; IPCC, 2014).

 

4. INFECTIOUS DISEASES ARE SENSITIVE TO CLIMATE CHANGE ELEMENTS

Climatic variables—including temperature, precipitation, wind, and humidity—have direct and indirect impacts on the transmission dynamics of infectious diseases (Santra, 2016). Numerous studies demonstrate that environmental changes caused by climate shifts alter the epidemiology of infectious diseases. Vector-borne diseases (VBDs), such as malaria and dengue fever, are particularly climate-sensitive because their transmission cycles depend heavily on vector ecology and survival. For instance, flooding events caused by extreme rainfall can significantly increase the risk of water-borne diseases. A notable example is cholera, caused by Vibrio cholerae, which proliferates under conditions of poor sanitation and water contamination exacerbated by climate change. Similarly, rising sea levels and humidity shifts expand the habitats of disease vectors, creating new breeding grounds.

Climatic elements influencing VBDs include:

• Temperature: Moderate increases in temperature enhance vector survival, reproduction, and biting rates, thereby accelerating disease transmission. Vectors in colder regions may expand into new geographical areas as warming creates suitable conditions. However, extreme heat may also reduce vector survival, forcing migration or adaptation to new ecological niches.
• Precipitation: Increased rainfall can promote outbreaks by expanding larval habitats and creating new breeding sites, particularly for mosquito species. Conversely, drought conditions may also drive humans and vectors into closer contact around limited water sources, further promoting disease spread (McMichael et al., 2003; Al-Khatib, 2015).
• Humidity and sea level: Elevated humidity favors vector activity and disease persistence, while rising sea levels reshape ecosystems, enabling vectors to thrive in previously unsuitable zones.

 

In essence, climate change reshapes the geographical distribution, abundance, and seasonal activity of disease vectors, ultimately altering patterns of infectious disease transmission.

 

5. VECTOR-BORNE DISEASES AND CLIMATE CHANGE

A vector serves as the primary mechanism for transmitting infectious diseases from one host to another. Vector-borne diseases (VBDs) are those illnesses that are spread by small animals or arthropods. Broadly, their transmission cycles can be categorized into two types: human–vector–human transmission (anthroponotic infections) and animal–vector–human transmission (zoonotic infections). Examples of anthroponotic infections include malaria, yellow fever, and dengue fever, while zoonotic infections include Lyme disease, hantavirus infection, and the majority of arboviral diseases (Al-Khatib, 2015; European Union, 2018). Anthroponotic infections require humans to act as the sole reservoir of the pathogens, thereby facilitating transmission between humans and vectors. In contrast, zoonotic infections rely on animals as their primary reservoirs, with humans functioning as incidental or spillover hosts. In such cases, humans typically contribute minimally to the overall transmission cycle, as pathogen levels in human populations remain relatively low. In general, the transmission of vector-borne diseases depends on three fundamental components: (i) a susceptible host population, (ii) a competent vector (most often arthropods), and (iii) a pathogenic agent, which may be a virus, bacterium, or parasite (Negev et al., 2015). For transmission to occur, specific ecological and environmental conditions must be met, and these conditions are increasingly being influenced by climate change in different parts of the world (WHO, 2015a, 2015b).

Climate change directly influences the abundance, survival, and distribution of vectors and reservoirs. For example, rising temperatures and altered precipitation patterns intensify the transmission of malaria, Lyme disease, schistosomiasis, and arboviral diseases such as West Nile virus. In addition, climate change facilitates the introduction and importation of vectors and pathogens into new regions, heightening the risks of dengue fever, chikungunya, and African trypanosomiasis. Pathogens themselves are also affected, with higher temperatures reducing incubation periods, altering transmission seasons, shifting geographic ranges, and sometimes increasing viral replication rates. Similarly, precipitation and humidity play critical roles in disease dynamics. Increased rainfall promotes vector survival, expands larval habitats, and creates new breeding sites. Heavy rainfall often synchronizes vector activity with host availability, enhancing transmission. Conversely, periods of low rainfall may drive the proliferation of container-breeding mosquitoes, while increased relative humidity prolongs vector survival and boosts transmission efficiency (WHO, 2015). In addition to environmental influences, human behavior acts as a crucial modifying factor in the epidemiology of vector-borne diseases. Climate change often magnifies the role of socioeconomic determinants such as migration, inadequate nutrition, poor sanitation, weak disease control programs, drug resistance, and land-use changes. These human-driven factors interact with environmental changes, shaping the prevalence and spread of infectious diseases across diverse settings.

 

6. SUGGESTIONS

Adaptation to the effects of climate change requires deliberate and collaborative human action (Morisetti & Brown, 2021). The following measures are particularly important in reducing the influence of climate change on vector-borne disease transmission.

 

6.1 Pest Control in Crops and Animals to Improve Public Health Nutrition

Food security is a cornerstone of public health, as adequate nutrition is essential for immune system strength and resilience against infections (FAO, 2011). However, agricultural pests continue to undermine crop yields, threatening the availability of nutritious foods. Controlling these pests is therefore critical. Several pest management methods are employed:

• Physical methods include manual removal, pest traps, burning, and flooding to destroy pest populations.
• Cultural methods modify environmental conditions to prevent pest growth, such as crop rotation, bush fallowing, controlled burning, and clearing of infested land (Areola et al., 2006; Bashar, 2025).
• Biological methods use natural enemies—such as parasitic wasps to eliminate stem borers—to control pest populations.
• Chemical methods employ pesticides and biocidal compounds to reduce pest infestations.

In addition to crops, animal-based foods provide proteins, vitamins, lipids, and essential minerals vital for preventing malnutrition. Diets that exclude animal products often fall short in supplying all necessary nutrients, further emphasizing the importance of healthy livestock management for human health (Sarkingobir & Miya, 2024; Bashar, 2025).

 

6.2 Vector Control Approaches

Vectors—including mosquitoes, lice, flies, and fleas—pose significant risks to public health by transmitting disease-causing pathogens. Among these, mosquitoes (particularly Anopheles, Culex, and Aedes species) are the most notorious, spreading malaria, yellow fever, encephalitis, filariasis, and dengue. Effective vector control measures include:

• Environmental management, such as draining swamps, ditches, and stagnant pools; eliminating unwanted containers; clearing vegetation around settlements; and spraying stagnant waters with kerosene or other larvicides.
• Chemical and biological control, including the sterilization of male mosquitoes and the application of insecticides.
• Waste management and sanitation, essential for controlling houseflies, which are reduced through proper garbage disposal, sewage management, and chemical treatment of larvae and adults.
• Rodent control, involving habitat destruction, proper food storage, and the application of rodenticides.

Equally important are personal hygiene practices that reduce exposure to pathogens. This includes regular washing of hands, face, and body parts such as armpits, groin, hair, nails, and teeth, especially before meals, after food preparation, and after using the toilet (Negev et al., 2015; Charles et al., 2020; WHO, 2015a).

 

7. CONCLUSION

In many developing regions, inadequate waste management and poor sanitation continue to worsen the burden of vector-borne and water-borne diseases. It is estimated that approximately 2.5 million people globally still lack access to safe systems for human waste disposal, a situation that contributes to high levels of morbidity and mortality, increased healthcare costs, and deeper cycles of poverty—particularly among vulnerable groups such as children, women, and the elderly. Addressing these challenges requires comprehensive public health interventions that focus on several key areas. First, hygiene education should be emphasized at both personal and community levels, including the construction of household and communal toilets as well as proper food hygiene practices. Second, improved water infrastructure is essential, particularly through the development of protected hand-dug wells and the expansion of pipe-borne water systems. Third, community-based vector control measures must be strengthened by eliminating environmental conditions that support vector breeding, applying insecticides where necessary, conducting household inspections, managing water storage properly, and encouraging the use of repellents and bed nets. Beyond these measures, broader social and environmental determinants such as overcrowding, poverty, and exposure to heat and humidity also need to be addressed. Ultimately, the effective control of vector-borne diseases depends on an integrated approach that brings together environmental management, public awareness, improved sanitation, and resilient healthcare systems.

Acknowledgments:

The authors would like to thank the University of Nairobi for providing institutional support and access to academic resources that facilitated this work. Special appreciation is extended to colleagues within the Department of Environmental and Public Health for their valuable insights and discussions.

Funding: This study did not receive financial support from any funding agency, whether public, private, or non-profit.

Conflict of Interest: The authors declare that there are no conflicts of interest regarding the publication of this paper.

Ethical Approval: As this paper is based exclusively on secondary literature and does not involve direct experimentation with humans or animals, ethical approval was not required.

 

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