Eastern Mediterranean Health Journal | All issues | Volume 31 2025 | Volume 31, issue 1 | Factors affecting establishment of dengue fever vectors in urban areas

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Factors affecting establishment of dengue fever vectors in urban areas

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Commentary

Hassan Nasirian1,2

1Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Islamic Republic of Iran (Correspondence to Hassan Nasirian: This e-mail address is being protected from spambots. You need JavaScript enabled to view it ; This e-mail address is being protected from spambots. You need JavaScript enabled to view it ). 2Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Islamic Republic of Iran

Keywords: dengue fever, vector-borne diseases, environment, One Health, Eastern Mediterranean

Citation: Hassan Nasirian. Factors affecting establishment of dengue fever vectors in urban areas. East Mediterr Health J. 2025;31(1):6–10.

https://doi.org/10.26719/2025.31.1.6. Received: 10/01/2024; Accepted: 25/08/2024

Copyright: © Authors 2025; Licensee: World Health Organization. EMHJ is an open access journal. All papers published in EMHJ are available under the Creative Commons Attribution Non-Commercial ShareAlike 3.0 IGO licence (CC BY-NC-SA 3.0 IGO; https://creativecommons.org/licenses/by-nc-sa/3.0/igo).

Dengue fever, caused by the dengue virus, is classified as a neglected, emerging, or re-emerging infectious disease and it creates a significant global health concern. The disease is transmitted to humans mainly through the bite of infected Aedes aegypti and Aedes albopictus. Dengue is the most rapidly spreading mosquito-borne disease, with a 30-fold increase in global incidence over the past 50 years (1). The risk of the spread of vector-borne diseases is higher in the WHO Eastern Mediterranean Region (EMR) due to its geographical and geopolitical situation, fragile health systems, complex humanitarian emergencies, and other socioeconomic factors. Dengue is one of the fastest-growing mosquito-borne viral diseases in the region and is endemic in at least 8 of the 22 countries and territories. Large dengue outbreaks have been reported in Afghanistan, Egypt, Pakistan, Sudan, and Yemen and the establishment of dengue fever vectors is influenced by a combination of ecological, environmental and socio-economic factors (2–10). Understanding these factors is crucial for effective control and prevention (11,12) and essential for implementing targeted interventions to reduce mosquito populations effectively (13–15).

Environmental factors

Dengue fever vectors are significantly influenced by various environmental factors, such as temperature, rainfall and humidity, which directly impact vector breeding and survival, making it crucial for their establishment and spread (10,16). Higher temperatures accelerate mosquito development, reducing their incubation period and increasing their biting frequency; a warm and humid climate provides an ideal breeding ground for the dengue virus vectors (3,4,17,18).

Another significant environmental factor is rainfall patterns (19). Excessive rainfall creates stagnant water pools, which serve as breeding sites for Aedes mosquitoes. These mosquitoes prefer to lay their eggs in clean water containers or artificial containers that collect rainwater, such as discarded tires, flowerpots or cans. Consequently, areas with high precipitation and inadequate waste and water management are more susceptible to dengue outbreaks (3,20). Out of 73 provinces examined in Thailand, an increase in temperature was associated with an increase in incidence in 9 provinces. In contrast, increased rainfall was associated with a decreased incidence in 7 provinces (21). Analysis by region shows that the incidence was negatively related to extra rainfall in the southern region, but was positively associated with elevated temperatures in the central and northern regions (21). The aggregate negative binomial regression model showed that precipitation, humidity and air pressure significantly influenced the spread of dengue fever in Sri Lanka (16).

Ecological factors, including vegetation cover, water availability and urbanization also affect vector abundance and distribution (2–5). Aedes aegypti adults fly passively as a mode of active ordinary dispersal or through transporting their eggs, larvae and adults. Aedes aegypti can spread over long spatial distances along trade routes of desiccated eggs or larvae and in containers such as cans, appliances, tires and discarded bottles, or by humans via goods (22). Approximately one-third of the annual tyre requirements of the Islamic Republic of Iran were imported from 15 countries, most of which were endemic to vectors (23).

Climate change impacts human behaviour and contributes indirectly to vector establishment (6,7,11,31). The spread of dengue fever vectors is influenced by climate change, as rising temperatures and changing precipitation patterns can expand the suitable habitats for these vectors (1,31,32). Climate change can exacerbate the situation by altering the geographical distribution of Aedes mosquitoes, allowing them to thrive in regions previously unsuitable for their survival (31,33). There is increasing evidence that recent climate change has already favoured the settlement of Aedes albopictus in temperate regions due to favourable overwintering and annual temperature conditions. The mosquito has not yet filled its potential ecological niche, and future climate change may sustain its establishment at higher latitudes in temperate regions (1). Pakistan has been the worst recipient of the consequences of climate change in the form of heavy rains that have led to widespread flooding across the country (34). The heavy rainfall pattern may be the main reason for the establishment of invasive dengue vectors in Pakistan.

Human factors

Urbanization plays a crucial role in the establishment of dengue fever vectors. Rapid urban growth often leads to inadequate housing, increased construction activities, improper waste management, and limited access to clean water (5,11,24,25). Urbanization often leads to the creation of artificial water containers, such as discarded tires and plastic containers, which provide ideal breeding grounds for mosquitoes. Urban areas often have a higher population density and limited access to proper sanitation services, further exacerbating the risk of dengue transmission. Deforestation contributes to the expansion of the geographic range for dengue vectors (5,7,11,20,25,26) because deforestation disrupts natural ecosystems and forces mosquitoes to seek alternative hosts closer to human settlements (4).

Human behaviour, such as improper waste disposal and poor sanitation, contributes to the proliferation of dengue fever vectors in urban areas (25,27). Human movement between areas with different levels of dengue transmission can introduce new vectors into previously unaffected regions (11,28,29). Aircraft and ships are believed to be directly responsible for rapid Aedes aegypti expansion. It invaded tropical Asia, where its dispersal has been associated with an increase in dengue fever incidence (30). At the end of 2013, in Dire Dawa, East Ethiopia, 40 of the 9258 suspected dengue fever cases were confirmed. Water stored in containers for long periods, extended rainy season and ambient relative humidity and temperature favour vector breeding. Because Dire Dawa is an industrial and tourism centre, it is preferred by visitors from neighbouring countries (Djibouti and Somalia) for temporary stay during the hot season. Many people also migrate to the town in search of jobs related to railway construction, and if these individuals are infected with the dengue virus they may transmit the disease through vector bites (19).

As urbanization continues to expand, the movement of people and goods contributes to the spread of dengue fever vectors to urban areas (36). The rate of vector-borne diseases has increased recently due to changes in human habitats, climate change, deforestation, the El-Nino phenomenon, physio-environmental factors such as land use or land cover types, changes in food production practices, and increased population movement (9,37). There was a consistent association between urbanization and the distribution and density of Aedes mosquitoes in 14 of 29 studies and a strong relationship between vector abundance and disease transmission in 18 studies. In 15 of the studies, a human population density of more than 1000 inhabitants per square kilometre was associated with increased levels of arbovirus diseases (36). Urbanization substantially increased the density, larval development rate and adult survival time for Aedes albopictus, which in turn potentially increased the vector capacity and, therefore, disease transmissibility (26).

Socioeconomic factors

Socioeconomic factors contribute to the establishment of dengue fever vectors by influencing human behaviour and living conditions (2–5). Poor communities often lack resources for basic sanitation and health care services, making them more vulnerable to dengue transmission. Limited access to healthcare facilities may delay diagnosis and treatment, allowing infected individuals to serve as reservoirs for further vector propagation.

Efforts to mitigate the establishment of dengue fever vectors must consider the role of globalization in facilitating the spread of these vectors across borders (35). International travel and trade can inadvertently transport vectors to new regions, contributing to the global expansion of dengue fever (30,33). The interconnected nature of modern transportation systems can aid the rapid dissemination of the virus, emphasizing the need for coordinated international efforts to address this public health concern. A combination of these factors creates a conducive environment for the establishment and spread of dengue fever vectors in urban areas.

Challenges of implementing dengue control programmes

Many challenges can impact dengue vector control programmes. A study in Hanoi, Vietnam, highlighted lack of interest, local community dependency on the health sector, lack of enthusiasm among local organizations and community leaders, poor communication by health authorities, low awareness and preparedness at community level, lack of detailed control policy guidelines, low enforcement of related policies, and limited budget (38).

The EMR already suffers from extreme temperature and precipitation fluctuations, as well as scarcity of natural water and agricultural land (40). Climate change is the greatest threat to global health, and health professionals in the region are already responding to the harms to health caused by this unfolding crisis (41). There are five key ways that the world can better adapt to the climate crisis: building climate-resilient infrastructure, developing early warning systems, restoring ecosystems, improving water supplies and security, and implementing long-term planning (42). Delays in addressing the interlinkages between climate and health will undermine decades of progress in public health (41).

Prevention of vector establishment

Efforts to control dengue fever vectors should focus on the reduction of mosquito breeding sites (38), including regular removal of stagnant water from artificial containers and promoting proper waste disposal practices. Public awareness campaigns can help educate individuals on the importance of maintaining clean and sanitized living environments that will minimize human-mosquito contact.

Collaboration with urban planning authorities is essential in designing and constructing mosquito-resistant infrastructure that can help control dengue fever vectors (39). This can involve incorporating features such as proper drainage systems and mosquito-proof water storage facilities into urban development projects. To build settlements that are resilient to Aedes-borne diseases, vector control experts should reach out and work with urban designers and developers. By creating safe, reliable and protective water supply systems, removing domestic waste and sealing or screening homes, we can prevent mosquito breeding and reduce their biting frequencies. Creating environments unfavourable for Aedes must be a priority when building safe, resilient and sustainable towns and cities (43). The world needs inclusive and sustainable urbanization as a milestone in the path towards socio-economic development.

Community engagement and participation are crucial in sustaining long-term vector control efforts, because local residents can play a significant role in identifying and eliminating potential mosquito breeding sites in their neighbourhoods. Participatory approach can promote changes in intersectoral management by facilitating social mobilization, which in turn leads to significant changes in dengue-related knowledge, attitudes and practices among the population and eventually more effective dengue fever vector control.

By addressing these multifaceted factors, public health authorities can work towards creating more resilient and dengue fever vector-free urban environments. Collaboration between countries and regions is essential for implementing effective surveillance and control measures for the prevention of dengue fever vector establishment in urban areas.

Intersectoral coordination

There is a need for intersectoral collaborations to develop, implement and evaluate dengue control initiatives at various levels of intervention (44). The recent global strategy for vector-borne disease control and prevention encourages intersectoral collaboration to increase cost-effectiveness and efficiency. Intersectoral collaboration can play an important role in reducing vector-borne diseases or vector densities. Collaboration can be at the local, national, regional, or international levels according to the burden and scope of interventions. Very few studies have assessed the contribution of intersectoral collaboration and how long intersectoral collaboration is needed to achieve sustainable integrated vector management (45). A study found that community participation increased collaboration considerably, although the costs increased by 26% when compared with interventions without community participation, and acceptability of interventions by communities increased from 66% to 78% (46).

Participatory approach can promote changes in intersectoral management by facilitating social mobilization, which in turn leads to significant changes in dengue-related knowledge, attitudes and practices among the population and eventually more effective dengue fever vector control. An intervention that adopted intersectoral planning for dengue prevention, focusing on source reduction, helped increase knowledge about breeding sites and disease symptoms significantly and the proportion of community members eliminating containers in and around their homes (47). An intersectoral collaboration in Asia involved 6 key actions: financial or technical support from within and outside the participating sectors; a clearly defined common interest that benefits all sectors; a division of workload and joint management to achieve a common goal; consistent coordination and communication among partner sectors; adaptability and flexibility in management; and capacity building for sustainable intersectoral partnership (48).

Funding: None.

Competing interests: None declared.

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