A nation in the grip of dengue: How climate, pollution, and urbanization are feeding a relentless killer – the mosquito

INTRODUCTION

Each year, mosquitoes wage a silent war – infecting about 700 million people and killing more than one million worldwide.^[1] Mosquito-borne viruses such as dengue, chikungunya, and Zika carry a staggering global economic toll: Over 45 years, in 166 countries, they have cost an estimated US $95 billion – and from 2013 to 2022, the cost rose 14-fold, far outpacing spending on prevention and control.^[2]

The global epidemic of dengue is believed to have emerged in Asia and the Pacific region during and following World War II.^[3] While malaria continues to strike hardest in Africa – with over 90% of cases and deaths occurring in the World Health Organization (WHO)-designated African nations, particularly in sub-Saharan regions^[4] – Asia bears the greatest burden of dengue, accounting for nearly seventy percent of all global cases.^[5] Within Asia, Southeast Asia faces the highest incidence, as noted in the British Medical Journal.^[6] Although the COVID-19 pandemic briefly disrupted this pattern, the strong resurgence of infections in its aftermath underscores the enduring and formidable threat of dengue across the region.^[7]

A nature journal study suggests that nearly three out of every five people could face the threat of dengue by 2080.^[8] Furthermore, the WHO warns that dengue alone sparks up to 400 million infections each year,^[9] casting its shadow over almost half of humanity.^[10] Over the past five decades, this mosquito-borne menace has surged alarmingly, its prevalence rising thirtyfold, with one in five severe cases proving fatal.^[11] In 2024, the disease leapt to unprecedented heights, infecting over fourteen million people worldwide^[12] – double the tally of the previous year^[13] and 12 times greater than a decade earlier.^[12]

EVOLVING EPIDEMIOLOGY OF DENGUE IN BANGLADESH

Since 2000, Bangladesh has experienced annual dengue outbreaks, with epidemics intensifying markedly in recent years. Dengue is now endemic across the country, with cases reported throughout the year. Incidence typically peaks between September and November, following the monsoon season. Historically, dengue cases in Bangladesh have been concentrated in the three largest cities – Dhaka, Chittagong, and Khulna. Between 2014 and 2016, fewer than 5% of individuals in the northern region showed evidence of prior dengue infection, compared with over 80% in Dhaka and Chittagong. Dengue fever in Bangladesh disproportionately affects young and middle-aged adults, is more prevalent among males in terms of total cases but results in a higher case fatality rate among females and older adults, and remains predominantly an urban phenomenon, with Dhaka City serving as the principal hotspot [Figure 1].

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Figure 1:

Mosquito breeding sites.

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ENVIRONMENTAL AND CLIMATIC DRIVERS

The recent dengue outbreaks, driven by shifting climate patterns, rapid urbanization, dense populations, insecticide resistance, and low public awareness, have severely strained Bangladesh’s healthcare system and economy. While climate change greatly influences dengue (Flavivirus) transmission, insecticide misuse and growing resistance also play critical roles.^[21] Experts warn that prolonged monsoons and poor waste management have created stagnant water and ecological imbalance, enabling mosquitoes to breed more extensively and intensifying the outbreaks.^[22]

Warmer temperatures accelerate mosquito aging, reducing their lifespan and altering infection patterns.^[23] Yet, over generations, heat-exposed mosquitoes evolve greater virus tolerance without losing vitality, a recent study finds.^[24] Global warming has become a “perfect storm” for mosquito-borne diseases, influencing every stage of transmission.^[25]

Although many attributed the 2025 outbreak to heavy rainfall, the persistence of dengue had already been evident, with over 320,000 infections and 1,700 deaths recorded in 2023 – figures considerably higher than those observed in 2025.^[26] Interestingly, a study conducted in Dhaka revealed that dengue cases actually declined with increasing levels of both rainfall and sunshine, contradicting common public perception.^[27]

CONSTRUCTION SITES AND HIGH-RISES: MAJOR BREEDING GROUNDS DRIVING DENGUE IN DHAKA

Dhaka’s rapid and largely unplanned urban expansion has transformed the city into a highly conducive environment for Aedes mosquito proliferation. Numerous under-construction buildings, left exposed to the elements, now serve as prime breeding grounds for the vectors of dengue. Surveys indicate that, in the decade preceding 2016, an average of 95,000 new structures were erected annually within the jurisdiction of the Rajdhani Unnayan Kartripakkha. Over the subsequent 15 years, at least 64,000 additional buildings were constructed across the capital.^[53,54] In July 2020, inspections conducted by the Dhaka North City Corporation (DNCC) revealed that nearly 70% (8,764 out of 12,619) of homes and construction sites surveyed across 55 wards harbored potential Aedes breeding sources.^[55] These inspections were carried out in collaboration with the National Malaria Elimination and Aedes Transmitted Disease Control Program under the DGHS.

The following year, the situation deteriorated further. A 2021 DGHS study covering 70 areas of Dhaka reported alarming Aedes densities, with the Breteau index – the number of water-holding containers infested with larvae per 100 houses – rising to 23.3 in Lalmatia and Iqbal Road (Ward 32, DNCC) and 20.0 in Saidabad and Uttar Jatrabari (Ward 48, DSCC). High-rise buildings accounted for over 45% of breeding sites, followed by under-construction structures at nearly 35%.^[56] In 2024, the former Mayor of DSCC warned that construction would be halted wherever Aedes larvae were detected and that dengue control drives would be launched in advance of the rainy season, alongside the government’s 7-year National Dengue Prevention and Control Strategy.^[57] The most recent pre-monsoon survey, conducted jointly by the DGHS Communicable Disease Control Program and the Institute of Epidemiology, Disease Control and Research, presents a similarly concerning picture: multistory buildings accounted for almost 60% of Aedes larvae, with a further 20% found in under-construction sites.^[58]

FROM NEGLECT TO EPIDEMIC: HOW POLICY FAILURES WORSENED DENGUE IN BANGLADESH

Bangladesh’s authorities have repeatedly failed to curb Aedes populations, relying on outdated chemical methods while neglecting root causes and community-level interventions. Government responses have remained fragmented. In 2023, authorities were unable to control Aedes mosquitoes, instead blaming households and imposing unethical fines. Mismanagement and flawed strategies have allowed dengue to spread unchecked, rendering prevention efforts largely symbolic. Transparency International Bangladesh identified key causes of high mortality, including insufficient hospital staff, delayed diagnoses, false-negative NS1 tests, weak vector control, and limited healthcare facilities outside Dhaka.^[59] Experts have warned that the absence of strategic planning, adherence to the WHO guidelines, and engagement of qualified professionals has further intensified Bangladesh’s dengue crisis. In 2024, South Asia endured its most severe dengue epidemic on record, with Bangladesh and India reporting thousands of deaths as hospitals became inundated. In FY 2024–2025, Dhaka South City Corporation expended <40% of its overall budget, despite increasing the allocation for mosquito control by 19 %.^[60] Furthermore, the two Dhaka city corporations spent more than Bangladeshi Taka (BDT) 1,000 crore (over $80 million) on mosquito-control programs and insecticide purchases, an expenditure that was effectively wasted. Weak implementation, poor coordination, outdated strategies, and shortages of chemicals and manpower severely undermined larviciding, mosquito control, and drain-cleaning operations.

CONCLUSION

In Bangladesh, the combination of rising temperatures, unplanned urban growth, and worsening pollution has created an ideal environment for mosquitoes, turning the country’s rapid development into a relentless struggle against its deadliest tiny predator. The persistent and evolving threat of dengue highlights the urgent need for timely hospitalization, as the disease can progress rapidly, alongside systematic research to understand how environmental pollution, climate variability, and widespread pesticide use are influencing viral resistance and mosquito dynamics. Media coverage has largely failed to convey the severity of the situation, and domestic research remains limited, often attributing outbreaks solely to erratic rainfall, monsoon shifts, and stagnant water. Yet studies from regions with similar dengue patterns point to overlooked factors, including air pollution, pesticide and microplastic resistance, and the complex interactions between urbanization and mosquito ecology. With low health literacy, even robust research seldom translates into public awareness or policy action, and progress in evidence-based studies remains slow. Coordinated efforts that integrate early clinical care with rigorous scientific investigation are therefore essential to reduce the growing public health burden of dengue.