Suddenly, dengue cases have surged in the coastal districts of Barguna and Barisal. In the last five and a half months of this year, Barguna has recorded the highest number of dengue cases. Deaths have also risen at an alarming rate. Entomologists and microbiologists believe this increase is linked to the rise in saltwater-tolerant Aedes mosquitoes in the coastal districts.
There are 19 coastal districts in Bangladesh. These include Barisal, Bhola, Barguna, Jhalakathi, Pirojpur, Patuakhali, Khulna, Bagerhat, Satkhira, Narail, Jashore, Cox’s Bazar, Chattogram, Chandpur, Feni, Noakhali, Lakshmipur, Shariatpur, and Gopalganj. Researchers have been studying these districts for over two decades, focusing on the spread of mosquito-borne diseases such as dengue and chikungunya as well as other illnesses driven by climate change. Recently, these areas have seen a notable spike in dengue outbreaks.
According to the Directorate General of Health Services (DGHS), one more person died of dengue in the last 24 hours. The deceased was from Chattogram division. During this time, Barisal division recorded the highest number of new cases—101 patients were admitted to hospitals there. Chattogram division reported 28 cases, Dhaka division five, Dhaka South City Corporation 19, and Dhaka North City Corporation 16.
As of Saturday (June 14), a total of 5,739 people have been infected with dengue this year. Among them, 59.3 percent are male and 40.7 percent are female. So far, 29 people have died of the disease. Last Friday, five deaths were reported in a single day—the highest single-day death toll from dengue so far this year.
DGHS analysis shows that half of all identified dengue patients are from the Barisal division. As of Saturday, the division had reported 2,589 confirmed dengue cases.
Barisal Divisional Health Officer Dr. Shyamal Krishna Mondal told Bonik Barta, “Among all the districts in our division, Barguna has the highest number of dengue patients. This trend was seen last year as well. But this year, the number is even higher. We’re spreading public health messages, urging people to destroy mosquito breeding grounds and avoid stagnant water anywhere. If this is not done, hospitals may soon exceed their capacity to accommodate patients.”
A report published in Nature India on April 24 highlighted that due to the impact of climate change, saltwater mosquitoes are emerging as a new threat in coastal areas. These mosquitoes, which breed in sea and estuary water, may be even more dangerous than freshwater mosquitoes in terms of spreading disease, the report claimed.
Despite the increase in saltwater mosquito populations, the authorities remain focused on controlling freshwater mosquitoes. The report warned that ignoring the saltwater variety could have serious consequences. As rivers in India change course, saltwater is mixing into them. This saline water has now reached deep into residential areas, creating a favorable environment for mosquitoes that transmit diseases such as dengue, chikungunya, Zika, yellow fever, and malaria. The report also noted that saltwater mosquitoes are reproducing faster and adapting quickly to these conditions.
Experts say the alarming rise in dengue cases in Bangladesh’s coastal districts is linked to the adaptability of Aedes mosquitoes. On this issue, Dr. Mahbubul Hasan Siddiqee, Professor of Microbiology at BRAC University, told Bonik Barta, “Aedes mosquitoes are typically known to breed in clean water. They are not supposed to breed in saline water. However, studies have found evidence of Aedes mosquitoes adapting to saline water in neighboring countries. This issue needs to be investigated further through extensive research. Due to climate change, all living organisms, including mosquitoes, are developing a certain level of adaptability. Mosquitoes are becoming tolerant not only to saline water for breeding, but also in carrying viruses.”
He warned that the presence of saltwater-tolerant Aedes mosquitoes could make the dengue situation in the country even more complex. “Mosquitoes in Dhaka and outside Dhaka won’t have the same characteristics. Likewise, mosquitoes that breed in freshwater and those in saline water are not the same either. The government must start working on this issue. Our country’s virus prevention and mosquito control methods are deeply flawed. Neither mosquitoes nor viruses are being effectively controlled under the current approach. If the wrong methods are applied to control mosquitoes in saline water as well, the entire mosquito management system in the country will collapse,” he said.
According to the Nature India research report, after the 2004 Asian tsunami, while investigating malaria risks, the Indian Council of Medical Research observed that Anopheles and Culex mosquitoes were breeding in seawater in villages across Tamil Nadu. This finding left scientists surprised. Recent studies have found that Aedes aegypti—the primary carrier of dengue—can lay eggs and mature from larvae to adult mosquitoes in both saline and mildly saline environments.
Professor Dr. Shefali Begum, Chair of the Zoology Department at the University of Dhaka, told Bonik Barta, “There is still no specific research in the context of Bangladesh on the adaptability of Aedes mosquitoes to saline water. There may be other reasons behind the dengue outbreak in coastal regions. Last year, we warned about the spread of dengue beyond Dhaka. There are many reasons why dengue can spread. One common cause is its gradual spread—first from Dhaka to nearby districts, then to the next districts—and eventually it has reached the coastal areas.”
She pointed out that the government has not paid enough attention to dengue management outside Dhaka. “For so many years, dengue was mostly confined to Dhaka. All resources were focused on mosquito control within the city. But for the last few years, cases from outside Dhaka were increasing. Now it’s time to take dengue management in other parts of the country seriously. The government also needs to work on why dengue is spreading in coastal areas and what kind of mosquito control methods are needed there. As academic researchers, we will also keep an eye on the matter,” she said.
When asked about the overall dengue situation in Barguna, Civil Surgeon Dr. Mohammad Abul Fattah said, “So far this year, 1,759 people in this district have been infected with dengue. Five people have died. According to entomologists, Aedes mosquitoes used to breed only in clean water. Now they are breeding in dirty water too. Due to climate change, coastal areas are becoming more suitable for dengue. Especially rainfall, humidity in the air, temperature, and unclean surroundings are all helping the Aedes mosquito population grow.”