Can dual strategy contain dengue?

Bangladesh is facing renewed dengue concerns this monsoon as Dhaka’s two city corporations adopt contrasting mosquito-control strategies to curb the spread of Aedes mosquitoes.

While Dhaka North City Corporation (DNCC) is relying on frequent field operations and rapid-response teams, Dhaka South City Corporation (DSCC) is targeting high-risk areas identified through scientific surveys.

Public health experts say both approaches have strengths, but warn that neither will succeed without sustained surveillance, proper implementation and public participation.

Following an increase in mosquito infestation, DNCC has directed its mosquito-control teams to carry out operations three times a day.

Larviciding is conducted in the morning to destroy mosquito larvae, followed by additional drives in the afternoon and evening. Fogging may continue at night during periods of high mosquito activity.

The corporation has also formed special Quick Response Teams to respond to sudden mosquito outbreaks and plans to continue operations even on weekly holidays.

Officials believe the strategy will help reduce adult mosquito populations and enable rapid responses to public complaints.

However, experts caution that fogging and insecticide spraying provide only temporary relief unless residents and property owners regularly remove stagnant water where Aedes mosquitoes breed.

DSCC, meanwhile, has adopted a survey-based strategy following a pre-monsoon assessment conducted jointly with the Communicable Disease Control unit of the Directorate General of Health Services (DGHS).

The survey identified Aedes mosquito risks in 63 of the corporation’s 75 wards, with 27 wards classified as highly vulnerable. Based on the findings, DSCC has launched a special crash programme focusing on the worst-affected areas.

Its teams are inspecting rooftops, unused water tanks, air-conditioner trays, flowerpots, construction-site basements and other places where rainwater accumulates.

The survey also found that dengue risk is no longer confined to slums or low-income communities, with modern residential buildings and construction sites emerging as significant breeding grounds.

The main difference between the two approaches lies in how they identify and respond to dengue risks.

DNCC emphasises frequent operations and rapid interventions, while DSCC concentrates resources on scientifically identified hotspots.

Experts believe the strongest response would combine DNCC’s operational intensity with DSCC’s data-driven targeting.

Chief Health Officer of DNCC Brigadier General Imrul Kayes Chowdhury told The New Nation that weather remains an important factor in dengue transmission but said the current heavy rainfall is not expected to significantly increase the spread of Aedes mosquitoes.

He said four dengue virus serotypes — DENV-1, DENV-2, DENV-3 and DENV-4—cause most infections. Among them, DENV-3 is considered the most dangerous, although he does not expect widespread transmission of that strain at present.

Kayes also said the City Corporation and the Ministry of Health had made significant progress in dengue control over the past two years.

Public health expert Dr Kasedul Islam Nayan of Sher-e-Bangla Medical College told The New Nation that fogging mainly kills adult mosquitoes and has little effect on larvae developing in water-filled containers.

He warned that survey-based programmes would also lose effectiveness unless authorities regularly update field data and monitor whether breeding sites have been properly cleared.

Bangladesh has experienced repeated dengue outbreaks since the disease was first recorded in the 1960s.

The first major epidemic occurred in 2000, when the country reported 5,551 cases and 93 deaths. In 2019, reported infections exceeded 100,000, with Dhaka remaining the epicentre.

The country’s worst outbreak came in 2023, when 321,179 confirmed dengue cases were recorded, according to DGHS data.

Between 1 January and 7 August that year alone, health authorities reported 69,483 laboratory-confirmed cases and 327 deaths, highlighting dengue’s transformation into a persistent national public health challenge rather than a seasonal disease.

Research using the XGBoost forecasting model projects Bangladesh could record between 35,297 and 330,242 dengue cases annually between 2024 and 2028, underscoring the continuing risk of major outbreaks.Globally, dengue has spread rapidly over the past two decades.

According to the World Health Organization, reported cases increased from around 505,000 in 2000 to 5.2 million in 2019. The disease is now endemic in more than 100 countries, with Asia accounting for about 70 per cent of the global burden.

Climate change, rapid urbanisation, unplanned construction, poor waste management and irregular rainfall have all contributed to the growing threat. Health experts say Bangladesh can reduce dengue infections this monsoon if authorities act before transmission peaks.

They stress that the two city corporations must work closely with DGHS, hospitals and local communities, while residents should regularly remove stagnant water from rooftops, water tanks, flowerpots, air-conditioner trays and construction sites.

Without sustained surveillance, elimination of breeding sources and active public cooperation, experts warn that mosquito-control drives alone are unlikely to prevent another major dengue outbreak.