As Bangladesh spent another year in the grip of the coronavirus pandemic, the prevalence of a familiar foe, dengue, has added further strain on an already overstretched public health system.
But this time, the mosquito-borne viral infection wasn't confined to Dhaka, nor was it prominent only during the monsoon, says a bdnews24.com report.
With climate change affecting weather patterns, particularly rainfall, dengue now poses a year-round threat, according to experts.
Moreover, rapid and uncoordinated urbanisation has created more breeding grounds for the Aedes mosquito, the vector for dengue.
According to the Directorate General of Health Services (DGHS), 580 of the 1,172 dengue patients in December were from Dhaka, while the other districts accounted for the remaining 592 cases.
As many as 28,394 patients were hospitalised for dengue across the country as of Dec 29. The disease has claimed 104 so far this year. At least 4,783 of those patients were from outside Dhaka.
Manoj Das, a development worker at a Rohingya camp in Cox's Bazar's Ukhiya, contracted the disease a week ago. He is now on the mend after receiving treatment.
At least 13 of his colleagues in the camp and four Rohingya refugees also came down with dengue fever, he said. He believes the vector carriers managed to find its way to Ukhiya from Dhaka.
"I have been living in Ukhiya since my childhood. We never had any dengue patient here, but now we do," he said. The number of patients could be higher if more tests were done, he added.
The Aedes aegypti and Aedes albopictus mosquitoes are responsible for dengue, with the former mostly prevalent in Dhaka and other big cities. The Aedes albopictus is more commonly found in rural areas.
Usually, dengue fever occurs from March to September, but after 2014, Bangladesh has been experiencing cases throughout the year.
Since 2016, dengue patients have been admitted to hospitals every month, according to the DGHS.
Although March to September is supposed to be the peak season for the illness, it is now prolonged due to the untimely rainfall, said Dr Be-Nazir Ahmed, former director of the DGHS.
"Rainfall is not occurring during the usual cycles due to the climate change. It rains in December, too. When it rains with some intervals, it creates more breeding grounds for the Aedes mosquito."
Outside Dhaka city, the Gazipur district recorded the most cases of dengue in the country with 1,124 from January to Dec 29. Cox's Bazar logged 342 cases, the second-highest among the districts. The number of cases in the rest of the country outpaced that in Dhaka on 11 different days in December, according to the DGHS.
Dengue cases found outside Dhaka in December 2021
Asked why the disease is becoming more prevalent outside Dhaka, Dr Be-Nazir pointed to the unplanned urbanisation occurring in other parts of the country.
"Different types of vehicles are used in rural areas and their tyres are discarded everywhere. As there are quite a number of construction works being done in rural areas, more places are found to have stagnant water bodies."
Stagnant water makes for an ideal breeding ground for the aedes mosquito, he said, adding better connectivity with Dhaka has been another factor behind the spread of the disease.
“Mosquitoes can go to other parts of the country when a bus or coach is running from Dhaka to that place.”
Aside from the breeding of mosquitoes, dengue patients travelling from one place to the other are carrying the pathogen with them. Therefore, a life cycle of dengue vectors is created there, he said.
As many as 24, 263 people contracted dengue in six years from 2013 to 2018, according to government data.
Among them, 37 patients were from outside Dhaka in 2016, 116 in 2017 and just 5 patients in 2018.
At least 131,153 people were diagnosed with dengue from Jan 1 to Dec 14, 2019, with Dhaka responsible for 76,645 cases.
In 2020, a total of 1,405 people contracted dengue, 1,224 of whom were residents of Dhaka. No records of dengue patients outside Dhaka between 2013 and 2015 were available.