Climate, urbanisation, and governance: Bangladesh’s triple dengue challenge

Dengue is no longer a seasonal illness in Bangladesh; it has evolved into a year-round public health crisis. Over the past decade, the epidemiological pattern of the disease has changed significantly. While previously confined to the months between June and September, infections now commonly extend from October through to January.

As of 31 October 2025, official records show that Bangladesh has registered 69,862 dengue cases, 278 fatalities, and 66,802 patient recoveries. These statistics are a clear indication that the outbreak is still far from being contained, and experts from Jahangirnagar University anticipate that dengue transmission will persist throughout November.

Demographically, 65.2% of cases are male and 34.8% are female. The most affected age group is consistently 16–25 years, encompassing mainly students and the working urban youth.

Worryingly, the death rate shows a narrow split (53.2% male and 46.8% female), with a clear and concerning concentration among children in the 0–5 years and 11–15 years age brackets, highlighting a distinct trend of child vulnerability.

The Dhaka Division continues to report the highest number of cases and fatalities, largely driven by factors such as dense population, poor sanitation standards, and the ineffective nature of current vector control operations.

The transmission of dengue is directly tied to meteorological variables. Changes resulting from climate change have seen rainfall extend until late October, dramatically prolonging the Aedes mosquito's breeding season. These mosquitoes typically lay their eggs in clean, stagnant water, such as in flowerpots, buckets, drums, discarded tyres, basement puddles, or at construction sites. The late deluge refills these habitats, enabling larvae to mature and consequently boosting the vector population even after the monsoon season has officially ended.

Additionally, Bangladesh's average temperature of around 20°C in November remains ideal for the breeding, viral incubation, and survival of the Aedes mosquito vector. This altered climate context has fundamentally created a "seasonal spillover effect," extending the reach of dengue well beyond the traditional rainy season.

A major barrier to dengue control is the lack of an effective administrative framework. Local government institutions—specifically city corporations and municipalities—conduct mosquito control activities sporadically and seasonally, rather than systematically. Efforts concerning larval surveillance and source reduction are often inadequate, and fogging operations frequently employ ineffective insecticides, which are applied at the wrong times and in the wrong locations. The combined shortages of trained entomologists and vector control specialists, coupled with poor planning and weak accountability, have rendered these crucial programmes largely ineffective, leading directly to residual mosquito breeding.

Research from Jahangirnagar University demonstrates that 70–80% of Aedes breeding sites are found within private and residential properties. However, many citizens wrongly assume that mosquito control is the exclusive duty of the government. Hence, essential weekly practices—including the cleaning of water containers, rooftops, garages, and flowerpots—have not been integrated into the routines of most households. 

Since Aedes mosquitoes complete their entire life cycle in a mere 5–7 days, weekly source reduction is crucial. Unfortunately, public awareness efforts remain reactive and seasonal, failing to provide the proactive, sustained push that is required.

While many assume dengue will subside in winter, urban ecology tells a different story. The basements of high-rise buildings, car-washing areas, construction sites, and water storage drums in zones facing water shortages all act as dry-season refuges for Aedes mosquitoes. Since these sources are not dependent on rainfall, mosquito breeding—and consequently, dengue transmission—can persist even during cooler months. Observations confirm that active Aedes populations remain in Dhaka's buildings throughout winter, sustaining viral transmission right through December and January.

The first step towards effective control must be the establishment of year-round larval and adult surveillance systems guided by scientific data. Every city corporation and municipality should be required to conduct ward-based larval surveys and create hotspot maps to pinpoint high-risk zones and periods. Furthermore, the regular monitoring of crucial larval indices—including the Breteau Index, House Index, and Container Index—should be made mandatory for every ward.

As shifts in rainfall and temperature are actively reshaping dengue seasonality, prevention strategies must proactively incorporate climate data and weather forecasts. An integrated Dengue Early Warning System needs to be jointly developed by the Meteorological Department and the Directorate General of Health Services (DGHS) to enable preemptive vector control operations in high-risk areas.

Mosquito control must be viewed as an Integrated Vector Management (IVM) process, and not simply as fogging. This necessitates providing city and municipal control departments with sufficient manpower, training, and modern equipment. Crucially, every ward should establish a Dengue Control Taskforce comprising health workers, sanitation officers, community leaders, and local representatives, supported by regular monitoring and accountability mechanisms.

Given that over 80% of Aedes breeding occurs inside homes and workplaces, community engagement is indispensable. Every household should be urged to inspect and clean potential breeding sites on a weekly basis. Nationwide awareness campaigns, such as the "Search and Destroy" initiative, should be revitalised, with schools, universities, mosques, temples, and local community organisations all actively participating in these vital drives.

Breaking misconceptions about dengue requires science-based education beginning at the school level. The national curriculum should include lessons on dengue prevention, mosquito biology, and public hygiene. Moreover, year-round awareness campaigns through television, radio, and social media should help make dengue prevention a daily habit rather than a seasonal response.

During peak transmission periods, hospitals face overwhelming patient loads. Every district and upazila hospital must have dedicated dengue corners, sufficient beds, trained staff, and strict adherence to fluid management guidelines. Private hospitals must also comply with the National Guidelines for Clinical Management of Dengue to prevent mismanagement and overmedication.

Sustainable dengue control demands strengthened research in entomology, virology, and ecology. Collaborative efforts between universities, research institutes, and the Directorate General of Health Services should prioritise studies on mosquito genetics, viral serotype evolution, and insecticide resistance. Bangladesh should also explore pilot projects using innovative technologies for vector suppression.

Poor waste management and stagnant water in discarded tyres, bottles, cups, and construction sites create ideal mosquito habitats. Urban authorities must enforce an Integrated Solid Waste Management Policy, ensure mandatory drainage systems in construction projects, and include mosquito prevention measures in the national building code.

In the era of Digital Bangladesh, technology must play a central role. A GIS-based dengue monitoring platform could allow citizens to report mosquito breeding sites or dengue cases through mobile applications or web portals, enabling rapid response and localised planning. Data from all city corporations should feed into a central database to guide national policy formulation.

Finally, dengue control must be integrated into a national public health policy rather than treated as a temporary project. The national budget should allocate specific funds for control programmes, research, awareness, and hospital preparedness. Both central and local authorities must establish systems of accountability and performance evaluation. Within the next five years, every city corporation should be required to implement a "Dengue-Free City Action Plan."

Dengue has become a persistent urban health crisis in Bangladesh. Combating it demands science-driven planning, citizen participation, and administrative accountability. As climate change reshapes our seasons, our response must be continuous, data-driven, and coordinated. It is time to move from neglect to preparedness — from reaction to prevention.

Sketch: TBS

Kabirul Bashar is a professor of Entomology at Jahangirnagar University.