Climate change and arboviruses_a growing threat to public health

Dear Editor,

The impact of climate change on public health is a multifaceted and increasingly urgent issue. Among the numerous health challenges it intensifies, the spread of arboviruses which are transmitted by arthropods such as mosquitoes and ticks emerges as a critical concern. Arboviral diseases, including dengue, Zika, chikungunya, and West Nile virus, are closely tied to environmental factors that are being dramatically altered by global climate change [1]. The relationship between climate change and arbovirus transmission is complex, involving interactions between temperature, precipitation, humidity, vector biology, human behavior, and socioeconomic conditions. Climate change is directly influencing the distribution, abundance, and seasonal activity of vectors. Temperature is a primary driver of vector distribution and viral replication within vectors. Mosquitoes, particularly Aedes aegypti and Aedes albopictus—primary vectors for dengue, Zika, and chikungunya—are highly sensitive to temperature changes. Warmer temperatures shorten the extrinsic incubation period (EIP) of viruses within mosquitoes, meaning that the virus matures faster, increasing the likelihood of transmission to humans. Studies have shown that the EIP for dengue virus is significantly reduced at higher temperatures, leading to a higher transmission rate [2,3]. Additionally, elevated temperatures expand the geographic range of vectors, allowing them to establish populations in previously cooler, temperate regions. This has been observed with the spread of Aedes albopictus into southern Europe and parts of the United States, regions where arboviral diseases were previously rare.

Changes in precipitation patterns further complicate the dynamics of arbovirus transmission. Increased rainfall can create ideal breeding sites for mosquitoes by generating standing water in natural and artificial containers. Conversely, drought conditions can also exacerbate mosquito proliferation as people store water in containers, which then serve as breeding sites. The relationship between precipitation and vector populations is nonlinear and context-dependent, with both excess and deficit of water potentially leading to increased transmission risk. For instance, the El Niño phenomenon, associated with both extreme rainfall and droughts in different regions, has been linked to significant outbreaks of dengue fever in Southeast Asia and South America. Humidity also plays a critical role in vector survival and activity. High humidity levels enhance mosquito survival and feeding frequency, thereby increasing the potential for arbovirus transmission. This is particularly relevant in tropical and subtropical regions where high humidity levels are common and where climate change is expected to exacerbate these conditions. However, even in temperate regions, shifts in humidity patterns due to climate change could alter the local epidemiology of arboviruses.

Urbanization and changes in land use, often driven by climate-related factors, are contributing to the increased transmission of arboviruses. Rapid urbanization, particularly in low- and middle-income countries, often results in the expansion of informal settlements with poor infrastructure. These areas lack adequate waste management and water supply systems, creating conditions conducive to mosquito breeding. The urban environment provides mosquitoes with an abundance of breeding sites, such as discarded containers, tires, and clogged drains. Moreover, the close proximity of humans in densely populated urban areas facilitates the transmission of viruses. For example, the explosive spread of chikungunya and Zika viruses in urban centers across Latin America in recent years highlights the role of urbanization in amplifying arbovirus transmission [4]. Human behavior and movement patterns are also critical factors influenced by climate change that affect arbovirus transmission. Migration, often driven by climate-related disasters such as floods, droughts, and extreme weather events, can lead to the displacement of populations into areas where they may be exposed to new vectors and viruses. Additionally, tourism and international travel contribute to the global spread of arboviruses, as travelers can carry viruses from endemic areas to new regions. The introduction of dengue, chikungunya, and Zika viruses into regions like the Americas and Europe has been facilitated by international travel, underscoring the importance of global mobility in the spread of these diseases [5]. Socioeconomic factors, which are often exacerbated by climate change, also play a significant role in determining the vulnerability of populations to arboviruses. Poverty, inadequate healthcare infrastructure, and limited access to clean water and sanitation increase the susceptibility of communities to arbovirus outbreaks. Furthermore, climate change disproportionately affects low- and middle-income countries, where the burden of arboviral diseases is already high. These regions often lack the resources to implement effective vector control programs or to respond rapidly to outbreaks, leading to higher morbidity and mortality rates. The intersection of climate change, poverty, and arbovirus transmission presents a significant challenge for global health equity.

The public health implications of climate-driven changes in arbovirus transmission are profound. Traditional surveillance systems may not be adequately equipped to detect and respond to the shifting patterns of arbovirus transmission resulting from climate change. There is a need for more dynamic and integrated surveillance systems that can rapidly adapt to changing environmental conditions and predict potential outbreaks. This requires the incorporation of climate data, vector monitoring, and advanced modeling techniques to forecast disease risk and guide public health interventions. Additionally, public health responses must be strengthened to address the increasing threat of arboviruses. This includes enhancing vector control strategies, such as the use of insecticides, biological control agents, and environmental management to reduce breeding sites. However, the effectiveness of these interventions may be compromised by the development of insecticide resistance and the adaptability of vectors to changing environments. Therefore, research and development of new tools, such as genetically modified mosquitoes and novel antiviral therapies, are critical. Public health education and community engagement are also essential components of a comprehensive response to the threat of arboviruses. Educating communities about the risks of arboviral diseases and promoting behaviors that reduce exposure to vectors are key to preventing outbreaks. This includes the use of personal protective measures, such as insect repellent and bed nets, as well as community-based initiatives to eliminate mosquito breeding sites.

In conclusion, climate change is amplifying the threat of arboviruses, with significant implications for global public health. The interplay between environmental, biological, and socioeconomic factors creates a complex and dynamic landscape for arbovirus transmission. Addressing this challenge requires a multifaceted approach that includes strengthening surveillance systems, enhancing vector control strategies, promoting public health education, and ensuring equitable access to healthcare. As the climate continues to change, the global health community must be proactive in mitigating the risks posed by arboviruses to protect the health and well-being of populations worldwide.

CRediT authorship contribution statement

Fatemeh Sadat Mousavi: Writing – original draft. Mohammad Shenagari: Writing – review & editing. Seyyed Mohammed Reza Hashemnia: Investigation. Milad Zandi: Conceptualization, Supervision, Writing – review & editing.

Funding

None.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Handling Editor: Patricia Schlagenhauf