KHULNA – Dengue infections are rising sharply across Bangladesh’s coastal belt, with more than 45,000 reported cases in 19 coastal districts, putting increasing pressure on upazila-level hospitals in the Khulna, Barishal and Chattogram regions. Public health experts are calling for further research to understand changing disease patterns and identify the factors driving the spread of the mosquito-borne disease.
According to the Directorate General of Health Services (DGHS), more than 40 percent of dengue patients hospitalised nationwide this year through October 23 were admitted to healthcare facilities in the 19 coastal districts. The figures highlight the growing burden of dengue beyond major urban centres. As of October 23, a total of 118,502 dengue patients had been hospitalised nationwide this year. Nearly 44,000 were admitted to government upazila hospitals and private healthcare facilities across the 19 coastal districts. During the same period, 361 patients died, while 112,111 recovered and were discharged from hospitals.
The affected coastal districts are Cox’s Bazar, Bagerhat, Barguna, Barishal, Bhola, Chandpur, Chattogram, Feni, Gopalganj, Jashore, Jhalakathi, Khulna, Lakshmipur, Narail, Noakhali, Pirojpur, Satkhira, Shariatpur and Patuakhali. The DGHS reported 1,512 new dengue hospital admissions across the country in the 24 hours leading up to October 23. In the Khulna division, 206 new patients were admitted during the same period, with no deaths reported. Since January 1, the Khulna division has recorded 18,734 dengue patients, of whom 17,112 have recovered and returned home.
Researchers, entomologists, physicians and public health specialists have identified several possible factors behind the growing number of dengue infections in coastal communities. These include limited previous exposure to the disease, inadequate drainage and sanitation, water storage caused by shortages of safe drinking water, and environmental conditions that favour mosquito breeding.
Dr. Banga Kamal Basu, a professor of surgery at Gazi Medical College Hospital in Khulna and a medico-social researcher, said further investigation was necessary to understand the changing pattern of dengue transmission. He suggested that the spread of dengue might involve factors that are not yet fully understood and stressed the need for more research into the disease’s transmission patterns.
Dr. Basu also said changes in dengue patterns could require a review of existing diagnostic approaches. He called for the establishment of specialised infectious disease isolation hospitals in every district to strengthen the country’s capacity to manage outbreaks.
Dr. Tanmoy Mallick, resident medical officer at Dacope Upazila Health Complex in Khulna, said coastal residents were generally less familiar with dengue prevention than people in urban areas, where the disease has circulated for years. He attributed part of the increase to relatively heavy rainfall this year, which has created additional breeding opportunities for Aedes mosquitoes in water-filled drains, canals, ponds and other locations across rural communities.
People in villages also tend to spend considerable time outdoors in the early morning and evening, potentially increasing their exposure to mosquito bites, he added. Dr. Rezaul Karim, health and family planning officer at Koyra Hospital in the coastal upazila of Koyra, said unhygienic surroundings and limited public awareness were contributing to the spread of dengue.
He identified water scarcity as another major concern. Because safe drinking water is not readily available in many coastal communities, residents often store rainwater and other water supplies in household containers. When left uncovered, these containers can become breeding sites for Aedes mosquitoes. Waterlogging in several unions of Koyra has further aggravated the problem, as inadequate drainage allows stagnant water to persist for extended periods.
Dr. Karim said awareness campaigns were underway to encourage residents to maintain clean surroundings and prevent water from accumulating in household containers, coconut shells and cattle drinking vessels.
Experts have also highlighted the possible role of Aedes albopictus, another mosquito species capable of transmitting dengue, in the growing number of infections in rural and coastal areas. Unlike Aedes aegypti, which is commonly associated with urban environments, Aedes albopictus can breed in vegetation, leaf axils, bamboo joints, coconut shells and other natural or artificial sites where water collects.
A survey conducted by the Institute of Epidemiology, Disease Control and Research (IEDCR) in Barguna in August found Aedes larvae in 26 of 134 water-holding containers inspected at homes and other establishments.
The survey recorded a Breteau Index of 53.06. The index measures the number of containers containing Aedes larvae per 100 houses inspected. A reading above 20 is generally considered an indication of a high risk of dengue transmission.
The findings identified water shortages, limited access to deep groundwater, household rainwater storage and insufficient awareness of mosquito breeding sites as possible contributors to the problem. The survey also found that approximately 58 percent of the Aedes mosquitoes identified were Aedes albopictus, while 42 percent were Aedes aegypti.
Entomologist Dr. Kabirul Bashar, a professor in the Department of Zoology at Jahangirnagar University and principal investigator of the Insect Rearing and Experimental Station (IRES), said commonly cited estimates of the two species’ relative contributions to dengue transmission were largely based on studies conducted in other countries.
Their behaviour and contribution to dengue transmission in Bangladesh could differ, making locally focused research essential, he said. “Perhaps Aedes albopictus has become capable of carrying a higher viral load. This requires detailed research,” Dr. Bashar said. He added that research into Aedes mosquitoes was beginning.
Dr. Sheikh Md. Mosharraf Hossain, director of health services for the Khulna division, said there was no specific dengue prevention programme dedicated to the coastal region, although mosquito-control and dengue prevention activities were being conducted nationwide. He also said research was ongoing. Dr. Sujat Ahmed, deputy director of Khulna Medical College Hospital, said Aedes mosquitoes reproduce in stagnant water during and after the rainy season.
He observed that mosquitoes, which were previously considered more active in biting during the daytime, now appeared to be biting people during both daytime and nighttime hours. Meanwhile, government agencies and other organisations have intensified mosquito-control operations, including insecticide spraying in coastal districts and other parts of the country.
Historical figures underline the growing importance of dengue in coastal Bangladesh. In 2023, the 19 coastal districts recorded 97,552 cases out of 321,179 nationwide, accounting for approximately 30.4 percent of the national total.
In 2025, the same districts recorded 35,511 hospitalised patients out of 102,358 nationwide, or around 34.7 percent. The 2025 figures cover the entire year, while the current year’s figures are available only through October 23, so the periods are not directly comparable. Experts say the rising burden of dengue in coastal communities calls for more extensive research into mosquito species, local transmission patterns and environmental risk factors.
They have also stressed the importance of improving drainage systems, ensuring safer household water storage, strengthening mosquito surveillance and expanding public awareness campaigns tailored to the needs of coastal residents. As dengue increasingly affects communities outside major cities, health specialists say locally targeted prevention strategies and evidence-based interventions will be crucial to reducing infections and preventing further deaths.
