The dengue situation in the country’s coastal belt has taken a serious turn, with reported cases in 19 coastal districts exceeding 45,000 as of October 23 this year, putting growing pressure on upazila hospitals across the Khulna, Barisal and Chittagong regions.
In view of the current trend, experts have stressed the need for more research to understand the disease pattern.
More than 40% of all dengue patients hospitalized in the country this year as of October 23 were admitted to hospitals in the 19 coastal districts. More than 34% of the country’s dengue deaths were also recorded in these districts, according to the Directorate General of Health Services (DGHS).
The 19 affected districts are Cox’s Bazar, Bagerhat, Barguna, Barisal, Bhola, Chandpur, Chittagong, Feni, Gopalganj, Jessore, Jhalakathi, Khulna, Lakshmipur, Narail, Noakhali, Pirojpur, Satkhira, Shariatpur and Patuakhali.
According to the DGHS, 1,512 new dengue patients were admitted to hospitals across the country in the 24 hours leading up to October 23.
As of October 23, a total of 118,502 dengue patients had been admitted across the country. Of them, nearly 44,000 were admitted to government upazila hospitals and private facilities in the 19 coastal districts. During the period, 361 patients died, while 112,111 were discharged from hospitals.
Meanwhile, 206 new patients were admitted in Khulna division, with no deaths recorded in the 24 hours leading up to October 23.
Since January 1, a total of 18,734 dengue patients have been reported in the division, while 17,112 have recovered and returned home.
Researchers, entomologists, physicians and public health experts have pointed to several possible factors behind the spread, including the virus reaching coastal areas with limited previous exposure, water storage due to shortages of safe drinking water, poor drainage and sanitation, and environmental conditions favorable for mosquito breeding.
In 2023, coastal districts accounted for 97,552 of the country’s 321,179 dengue patients, or 30.4%.
Last year, 35,511 patients were hospitalized in the 19 districts out of a national total of 102,358, representing about 34.7%. The 2025 figure covers the entire year, while this year’s data are available only up to mid-October.
Dr Banga Kamal Basu, professor of surgery and a medico-social researcher at Gazi Medical College Hospital in Khulna, said the spread might not be caused solely by mosquitoes, emphasizing the need for further research to understand the pattern.
Stressing the need for more research into dengue, he said the disease pattern might have changed, requiring changes to the system of pathological testing.
Dr Basu, also a public health specialist, called for the establishment of hospitals specializing in the isolation and treatment of epidemic diseases in every district across the country.
Dr Tanmoy Mallick, resident medical officer at Dacope Upazila Health Complex in Khulna, said coastal residents were generally less aware of dengue than urban populations, where the disease had been prevalent for years.
He said relatively heavy rainfall this year had created more breeding opportunities for Aedes mosquitoes in water-filled drains, canals, ponds and other places in rural areas.
People in villages are also frequently outdoors in the early morning and evening, when Aedes mosquitoes are active, increasing their exposure to bites, he said.
Dr Rezaul Karim, health and family planning officer at Koyra Hospital in the coastal upazila, attributed the spread partly to unhygienic surroundings and limited public awareness.
He also identified water scarcity as a major concern in coastal areas. Many residents store rainwater and other available water in containers because of shortages of safe drinking water. Such containers can become breeding grounds for Aedes mosquitoes if left uncovered.
He also pointed to waterlogging in several unions of Koyra, where inadequate drainage allows water to remain stagnant for extended periods.
Karim said awareness campaigns were being conducted to encourage residents to maintain clean surroundings and prevent water from accumulating in household containers, coconut shells and cattle drinking vessels.
Experts have also identified the spread of Aedes albopictus, another dengue-transmitting mosquito species, as a possible factor.
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 water-holding sites in rural and semi-urban areas.
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 examined at homes and other establishments.
The Breteau Index, which measures the number of containers containing Aedes larvae per 100 houses inspected, stood at 53.06. A reading above 20 is generally considered a warning of a high risk of transmission.
The survey identified water shortages, limited access to deep groundwater, household rainwater storage and a lack of awareness about mosquito breeding sites as possible contributors.
The Barguna survey found that around 58% of the Aedes mosquitoes identified were Aedes albopictus, while 42% were Aedes aegypti.
Entomologist Dr Kabirul Bashar, a professor in the Department of Zoology at Jahangirnagar University, said commonly cited estimates of the relative roles of the 2 species in dengue transmission were largely based on findings from other countries.
Their behavior and contribution to transmission in Bangladesh might differ, making further research necessary, he said.
“Perhaps Aedes albopictus has become capable of carrying a higher viral load. This requires detailed research,” he said.
Bashar, also the principal investigator of the Insect Rearing and Experimental Station (IRES), said: “We are beginning research on Aedes mosquitoes.”
Director of Health Services for Khulna division Dr Sheikh Md Mosharraf Hossain said there was no specific program focused on the coastal region, although dengue prevention activities were being carried out nationwide. He also said research was ongoing.
Deputy Director of Khulna Medical College Hospital (KMCH) Dr Sujat Ahmed said Aedes mosquitoes reproduce in stagnant water during and after the rainy season.
The mosquitoes, which previously mainly bit people during the daytime, now appeared to be biting both during the day and at night, he added.
Meanwhile, the government and other agencies have intensified mosquito-control operations, including insecticide spraying in the coastal belt and across the country.
Experts said the rising number of infections and deaths underscored the need for further research into the factors driving transmission in coastal districts, alongside improved drainage, safer water storage, mosquito surveillance and public awareness campaigns tailored to local conditions.