The Mongla Upazila Health Complex in Bagerhat has 50 beds. On 18 October, 31 dengue patients were being treated there. So far this year, 532 dengue patients have been admitted to the facility.
Md Shaheen, the upazila health and family planning officer in Mongla, said the hospital never had so many dengue patients admitted before. He added that the number of hospital admissions did not fully reflect the severity of the outbreak. The situation was even worse, he said.
The situation in Mongla reflects the reality across the country’s coastal belt. Dengue was once largely confined to the capital, but it has now spread nationwide. However, the disease has spread more extensively in coastal areas. Nearly 40 per cnet of all dengue patients admitted to hospitals across Bangladesh this year have been in 19 coastal districts.
Since dengue re-emerged in the country in 2000, no other period has seen such a high proportion of hospital admissions in coastal districts.
The government has not provided any specific explanation for the high incidence of dengue in coastal areas. Researchers, entomologists, physicians and public health experts have offered several possible explanations.
Some of the factors, according to them, are coastal areas are relatively new transmission zones for dengue, known in epidemiology as “virgin areas”; water stored because of shortages of safe drinking water; poor sanitation and waterlogging in the absence of elected local government representatives; and natural breeding grounds in agricultural settings.
40pc of dengue patients in coastal districts
The spread of dengue beyond Dhaka and other major cities has been a subject of discussion for several years. District-level data from the Directorate General of Health Services (DGHS) also show a rising number of cases in coastal districts.
The 19 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 survey noted that shortages of safe drinking water and limited access to deep groundwater had led local residents to store rainwater in drums. Stagnant water around homes and a lack of awareness about Aedes breeding sites could also be contributing to mosquito proliferation.
According to DGHS data, as many as 43,148 dengue patients had been admitted to hospitals in these 19 districts up to 17 October this year, accounting for 39.6 per cent of all hospitalised cases. During the same period, hospitals across the country saw an admission of a total of 110,312 dengue patients.
In 2023, hospitals in coastal areas admitted 97,552 dengue patients out of 321,179 cases nationwide, which was 30.4 per cent of the total.
In 2025, coastal districts recorded 35,511 hospital admissions, while the nationwide total was 102,358. The coastal share stood at around 34.7 per cent. However, the 2025 figures cover the entire year, whereas this year’s figures extend only to mid-October.
Public health expert Mushtuq Husain told Prothom Alo, “The figures we have for coastal areas are based on the locations of hospitals. They do not always tell us where patients live or where they contracted the infection. In reality, the number of cases in coastal areas is likely to be much higher.”
Why is dengue spreading so widely along the coast?
An analysis of data from Mongla Upazila Health Complex found that more than 55 per cent of its dengue patients came from Mongla municipality.
Upazila health officer Md Shaheen said coastal communities faced severe shortages of safe drinking water. Many people stored rainwater or other available water for later use. Since Aedes mosquitoes breed in clean water, he believed this was a major factor behind the outbreak in Mongla.
Waterlogging is also common in Mongla pourashava (municipality) and several union parishad headquarters because of inadequate drainage systems.
Shaheen said the pourashavas and union parishads currently had no elected representatives to oversee these issues. As a result, little was being done to address water that remained stagnant for long periods.
Dengue first emerged in Dhaka and gradually spread elsewhere. When transmission becomes widespread in one area, the virus finds new areas to spread to. Coastal regions offered favourable conditions for Aedes mosquitoes, which may explain the spread there, said entomologist Professor Kabirul Bashar.
In August this year, the Institute of Epidemiology, Disease Control and Research (IEDCR), under the DGHS, conducted a survey of Aedes mosquitoes in Barguna. Researchers examined 134 containers holding stagnant water at homes and other premises and found Aedes larvae in 26 of them.
The Breteau Index, which measures the number of containers containing Aedes larvae per 100 houses inspected, is an important indicator of mosquito infestation. A value above 20 is generally considered a sign of a serious situation. According to the survey, Barguna’s Breteau Index was 53.06.
The survey noted that shortages of safe drinking water and limited access to deep groundwater had led local residents to store rainwater in drums. Stagnant water around homes and a lack of awareness about Aedes breeding sites could also be contributing to mosquito proliferation.
Jannatul Ferdous, a senior scientific officer at IEDCR, told Prothom Alo that surveys had been conducted in Pirojpur as well as Barguna. Water shortages were a major factor, she said. However, Aedes mosquitoes were also found in large numbers in areca palm trunks and flower nurseries.
Unusually high presence of Aedes albopictus
There are two main types of Aedes mosquitoes that transmit dengue: Aedes aegypti and Aedes albopictus. The former is responsible for most dengue transmission. Yet despite the high number of dengue cases along the coast, surveys have found a significant presence of Aedes albopictus in the region.
For instance, the IEDCR survey in Barguna in August found that nearly 58 per cent of the Aedes mosquitoes identified were Aedes albopictus, while 42 per cent were Aedes aegypti.
Globally, Aedes aegypti is estimated to account for around 95 per cent of dengue transmission by these two species, compared with just 5 per cent for Aedes albopictus. Why, then, is dengue spreading so extensively along the coast?
Responding to the question, entomologist Kabirul Bashar said, “The information we have about the relative contribution of Aedes aegypti and Aedes albopictus to dengue transmission comes from experience in other countries. The situation in Bangladesh may be different. It is possible that Aedes albopictus has become a more significant carrier of the virus here. This requires detailed research.”
Dengue deaths also higher in coastal areas this year
So far this year, dengue has claimed 342 lives across Bangladesh. Of these, 117 deaths were recorded in hospitals in the 19 coastal districts. The actual number could be higher, as not everyone who dies in a Dhaka hospital is a resident of the capital; some may come from coastal areas.
Even based on the 117 recorded deaths alone, the 19 coastal districts account for around 34 per cent of the national total.
Despite the rising dengue burden in this environmentally vulnerable region over the past several years, the government has no special plan targeting the coastal belt. Nor has there been a concerted effort to prevent the deaths occurring there.
Professor Halimur Rashid, director of the disease control branch of the DGHS, told Prothom Alo, “Work to prevent dengue is being carried out across the country. However, it is true that there is no special programme targeting coastal areas.”
Public health expert Mushtuq Hossain said, “Unfortunately, coastal areas have become major zones of infection over the past several years, yet I have not seen any specific plan for the region. The people of the coast are silent victims of the government’s overall indifference.”