Kolkata tamed dengue. Can Bangladesh learn how?

Dengue has changed its address in Bangladesh. For years, we tended to think of it primarily as a Dhaka problem — a seasonal menace associated with the capital's crowded neighbourhoods, construction sites and stagnant water. 

That picture is now dangerously outdated. 

Dengue has spread across the country, increasingly affecting smaller towns and rural areas. In June this year, 78% of hospitalised dengue patients were reported from outside Dhaka. 

As Bangladesh struggles to contain the disease, perhaps we should look across the border. Kolkata, a city with climate, ecology, population density and many environmental characteristics similar to ours, has developed an interesting approach to dengue control.

Has Kolkata really "tamed" dengue? Yes, to an extent. But the success needs to be taken with a grain of salt. 

More importantly, there are lessons in how Kolkata organised its response that Bangladesh could use, particularly if we can adapt an urban model to a disease that has now spread throughout the country.

Don't wait for the epidemic

Perhaps the most important feature of the Kolkata approach is deceptively simple: dengue control is treated as a year-round municipal responsibility, not an emergency operation launched when hospitals begin filling up.

The Kolkata Municipal Corporation (KMC) organises vector control, control of mosquitoes and other organisms that transmit disease, across its 144 wards and 16 boroughs. Its system combines surveillance of fever cases, searches for mosquito larvae, household visits, elimination of breeding sites and rapid action when cases are detected. 

One particularly interesting initiative was to ask a basic question: Where are the mosquitoes likely to breed? 

In 2014, KMC prepared an extraordinary 9,048-page databank of potential mosquito-breeding sources across the city. It identified tens of thousands of open masonry tanks, uncovered overhead water reservoirs, construction sites, surface drains and other places where water could collect. 

Importantly, their locations were recorded so field workers could return and inspect them repeatedly. 

This may sound less glamorous than a new vaccine or sophisticated mosquito technology. But it embodies a fundamental public-health principle: know where the problem is, assign somebody to deal with it, and return to make sure it has been dealt with.

Kolkata also built a substantial field operation, with hundreds of teams conducting house-to-house surveillance and mosquito control, supported by rapid-action teams. Particular attention is paid to construction sites, where water accumulating in basements, lift shafts, drums and discarded materials can become breeding grounds for Aedes aegypti, the mosquito principally responsible for transmitting dengue.

We already know much of what Kolkata can teach us. The challenge is to put those lessons into practice, and sustain them year after year. Perhaps our biggest problem is no longer knowing what to do. It is our repeated failure to do it systematically, continuously and at scale.

This differs from relying excessively on fogging — spraying a fine mist of insecticide into the air to kill adult mosquitoes. Fogging may have a role during outbreaks, but it does not eliminate the water-filled containers where the next generation of mosquitoes is developing. 

Kolkata puts much greater emphasis on finding and destroying breeding sites before adult mosquitoes emerge.

Has it worked? The recent figures are impressive: Kolkata recorded 12,334 dengue cases between January and early November 2023. During the comparable period in 2024, the number reportedly fell to 1,316, and in 2025 to 1,106 — a reduction of around 91% between 2023 and 2025. 

But Kolkata has not declared victory. The year 2023 was exceptionally bad, making subsequent reductions look particularly dramatic. Dengue also fluctuates naturally because of rainfall, temperature, circulating virus strains, population immunity and other factors. 

The decline therefore cannot scientifically be attributed entirely to KMC's programme. Most importantly, Kolkata has not eliminated dengue. Cases continue to occur and high-risk areas remain under surveillance.

The Kolkata story is therefore not: "We found the formula and dengue disappeared." It is more modest, and more credible: a city repeatedly battered by dengue built a disciplined system for finding breeding sites, assigning responsibility, acting locally and maintaining prevention throughout the year.

That is the success Bangladesh should study.

Bangladesh's problem is now national

We obviously cannot reproduce Kolkata's municipal machinery in every upazila. But its principles are transferable: year-round surveillance, identification of breeding sites, rapid response when cases appear, source reduction rather than excessive dependence on fogging, clear responsibility and community participation.

Bangladesh therefore needs a tiered national dengue-control system. Dhaka, Chattogram and other large cities need permanent professional teams operating at ward level. Smaller municipalities need appropriately sized surveillance and vector-control teams. In rural areas, upazila health complexes, community clinics, union parishads, schools, mosques and community health workers could become part of the surveillance and prevention network.

When cases begin clustering in a locality, action should follow quickly. Where are they occurring? Where are the mosquitoes breeding? Who is responsible for eliminating those sites? And has someone returned to check?

A national strategy must result in intensely local action. Bangladesh has done this kind of scaling before. We have taken immunisation, oral rehydration therapy, family planning, tuberculosis treatment and other public-health interventions to millions of households. Government, NGOs and community workers have repeatedly demonstrated that relatively simple interventions can reach even remote villages when responsibilities are clear and communities are engaged.

Dengue requires a similar implementation mentality. Simply telling people "do not allow stagnant water" is not enough. Families need to know where dengue mosquitoes breed in their own surroundings and what they should do every week to eliminate those sites.

The Prime Minister's recent initiative is therefore encouraging. Launching a three-month nationwide dengue prevention and cleanliness campaign, he urged citizens to spend at least one hour every week cleaning their homes and institutions. 

Imagine schools, markets, mosques, community clinics, offices and local-government institutions participating in such a weekly routine: find standing water, empty or cover the container, and report breeding places that communities cannot remove themselves.

But the Kolkata experience offers an important caution: a campaign, however energetic, is not a system. Three months of mobilisation can provide the impetus, but dengue prevention must become a permanent, year-round responsibility.

Singapore and Vietnam: Complementary lessons

Two other Asian experiences complement Kolkata's lessons.

Singapore is using Wolbachia, a naturally occurring bacterium, to suppress dengue mosquitoes. Male Aedes mosquitoes carrying Wolbachia are released into neighbourhoods. These males do not bite; when they mate with wild females, their eggs do not hatch, gradually reducing the mosquito population. 

Singapore reports substantial reductions in mosquito populations and dengue risk in intervention areas. Bangladesh could consider carefully evaluated Wolbachia pilots. But Singapore itself stresses that this technology complements rather than replaces elimination of breeding sites.

Vietnam offers another lesson, perhaps especially relevant to rural Bangladesh. Some programmes used Mesocyclops, tiny, harmless freshwater creatures that eat mosquito larvae, in household water containers. 

Crucially, this was combined with mobilisation of local leaders, health workers, teachers and schoolchildren. Evaluations reported dramatic reductions in Aedes mosquitoes in participating communities. 

Singapore brings technology. Kolkata brings municipal organisation. Vietnam brings community mobilisation. Bangladesh may need elements of all three.

We have heard this before

None of this is entirely new to Bangladesh. Indeed, there is an uncomfortable sense of déjà vu or familiarity.

During the severe dengue outbreak of 2019, the then Local Government Minister led a five-member Bangladesh delegation to Kolkata specifically to learn how the city was controlling dengue. 

The delegation met Kolkata Mayor Firhad Hakim and senior KMC officials and was briefed on the city's approach. The minister praised what he saw and said Bangladesh would take similar steps. 

There were further exchanges between officials of the two cities, including discussions of Kolkata's year-round surveillance, monitoring and emphasis on destroying mosquitoes at their breeding sources.

The Business Standard was asking the same question at the time. In August 2019, it published "Dengue: What can we learn from Kolkata and Sri Lanka?", questioning our reliance on fogging and emphasising destruction of breeding grounds and community involvement. 

Four years later, TBS returned specifically to "the Kolkata model," again highlighting year-round monitoring, ward-level organisation, cleanliness and systematic searches for breeding sites. 

There were initiatives after the 2019 visit, but the central lessons were never institutionalised at the scale required. Bangladesh continued to experience increasingly severe dengue outbreaks, while mosquito control remained too often reactive, fragmented and dependent on seasonal drives.

We therefore do not need another study tour to Kolkata. We already know much of what Kolkata can teach us. The challenge is to put those lessons into practice, and sustain them year after year. Perhaps our biggest problem is no longer knowing what to do. It is our repeated failure to do it systematically, continuously and at scale.

An opportunity for the new government

This makes dengue an important early test for the new BNP government. Its election manifesto specifically promised a 'science-based mosquito-control programme' against dengue, malaria and chikungunya, while disease prevention and primary healthcare have been identified among the government's priorities. 

The opportunity is considerable. A government at the beginning of its term could make dengue control a matter of national performance and prestige: set measurable targets, establish responsibility from the centre down to the union, publish results, mobilise communities and insist that implementation continue throughout the year.

The Prime Minister's cleanliness campaign is an encouraging beginning. It also creates expectations. If the campaign is followed by permanent surveillance, local accountability and year-round source reduction, it could mark a genuine change from the episodic responses of the past. If attention fades once the immediate dengue season passes, we will have repeated an all-too-familiar cycle.

This need not be partisan. Controlling dengue is the kind of visible public good around which political parties, local government, professionals, NGOs and communities should be able to unite.

Bangladesh does not primarily lack knowledge about dengue. We know the mosquito, where it breeds and many of the measures needed to control it. Our challenge is converting that knowledge into thousands of small, repetitive actions carried out reliably across thousands of communities.

That is why Kolkata matters. Its most important innovation was not a miracle technology. It was an implementation system: map the breeding places, assign responsibility, inspect repeatedly, respond rapidly and keep doing it throughout the year.

Bangladesh should neither copy Kolkata mechanically nor romanticise its achievement. But Kolkata has demonstrated that dengue need not simply be accepted as an inevitable annual calamity.

The new government has an opportunity to show that Bangladesh, too, can turn knowledge into implementation. Success in bringing dengue under control would be more than a public-health achievement; it would be a visible demonstration that the government can deliver.

The Prime Minister's campaign can be an excellent beginning. The challenge is to turn that beginning into a durable system.

Because dengue has spread beyond our megacities, the response must extend from the ward to the union, from the city corporation to the village, and from the health ministry to the whole of government and society.

Dengue has gone national. Our response must do the same.

Sketch: TBS

Professor Mushtaque Chowdhury is the Convener of Bangladesh Health Watch and founding dean of the Brac University James P Grant School of Public Health.