A lack of initiatives by both of Dhaka city's corporations has helped the breeding of Aedes mosquitoes, causing a spike in dengue fever cases during the off-season.
Although the peak season of dengue fever epidemics is usually from June to September, the situation is different this year.
According to the Health Emergency Operation Centre and Control Room under the Directorate of Health, there have been 440 dengue cases in November – the highest in a single month this year.
It was 163 last month.
More than 93% of dengue patients are Dhaka city dwellers this time.
Currently, 88 patients are undergoing treatment for dengue fever across the country. Of them, 83 are in the capital, according to the Directorate of Health.
At least 22 new dengue patients were hospitalised in 24 hours till 8am on Wednesday. Of them, 21 are in Dhaka.
Public health experts fear many dengue patients might be undiagnosed as symptoms of the fever are quite similar to those of Covid-19.
Experts have observed that many under-construction sites in the capital, which have remained closed amid the pandemic, have become potential breeding grounds for Aedes larvae.
Further, stagnant water caused by the unusual rainfall in October is another reason for the rise in the number of mosquitoes.
They blame the city corporations for not taking the aforementioned factors into consideration and conducting special drives in September and October to control mosquito breeding.
According to vector surveillance of the entomology lab of Jahangirnagar University, the average density of mosquito larvae – using the Breteau Index, the number of positive containers per 100 houses inspected – was 11 in October and November.
Moreover, in some areas like in Uttara and Gulshan, it was higher than 20, which indicates an alarming possibility of the vector-borne disease spreading.
The study, led by entomologist Prof Kabirul Bashar of the university, covers six wards of the Dhaka North and South city corporations.
The areas are: Lalmatia, Mohammadpur, Gulshan, Banani, Bashabo, Khilgaon, Poribag, Shahbag, Shankhari Bazar, Patuatuli, Islampur, Kumartuli, Banglabazar, and Uttara.
Prof Kabirul told The Business Standard, "The main reason behind the rise of mosquito-borne dengue disease is a lack of proper initiatives of the city corporations after the end of the peak season. Many under-construction sites were closed during the pandemic. Water has been accumulating there and the stagnant water has become a breeding ground for mosquitoes."
Prof Kabirul has also pointed out that residents of some areas in Old Dhaka are suffering from a water crisis as they are getting water from WASA only two times every day.
"That is why people store water in their houses, which is another reason for mosquito breeding," he explained.
However, officials of Dhaka North and South city corporations said they are concerned about the mosquito breeding in under-construction sites.
Dhaka North City Corporation (DNCC) conducted four special operations from May to August to control the mosquito menace.
The special campaign was off for two months – September and October – as the peak season had ended.
Dr Md Khalequzzaman, associate professor at the Public Health and Informatics Department of Bangabandhu Sheikh Mujib Medical University (BSMMU), said the authorities of the city corporations should have thought about the untimely rains caused by climate change and taken action accordingly.
He also said the authorities concerned, including the city corporations, did not focus on dengue fever control properly amid the Covid-19 pandemic.
He suggested dengue screening alongside Covid-19 tests as the mosquito-borne disease has been on the rise.
However, Brig Gen Md Zobaidur Rahman, chief health officer, DNCC, denied the allegation of there being poor initiatives in the last few months.
He said the huge rainfall in October was responsible for the stagnant water, which became potential breeding sources of Aedes mosquitoes.
"Fourth generation larvicide Novaluron, imported from the United Kingdom, was sprayed on different mosquito breeding grounds during the recent special combing operation. The larvae of the places, where this larvicide is sprayed, cannot develop into adult mosquitoes. This insecticide remains effective for 90 days," said Brig Gen Md Zobaidur Rahman.
Meanwhile, Dhaka North City Corporation's ten-day-long special drive for mosquito eradication ended on 14 November.
During the drive, a total of around Tk22.83 lakh was realised as fines through mobile courts, mainly for getting larvae in different spots.
Entomologists say there are four important methods for controlling Aedes mosquitoes. The methods are: environmental management, biological control, use of insecticides, and involving citizens in the mosquito control programmes.
Until now, most attempts to destroy mosquitoes in Dhaka have relied solely on insecticides.
Malaria, dengue, chikungunya, Zika, and filariasis are the mosquito-borne diseases in Bangladesh while the vectors are Anopheles, Aedes and Culex mosquitoes.
Experts say there are 123 species of mosquitoes in the country, with about 14 varieties currently found in Dhaka.
In 2019, Bangladesh was hit by the worst dengue outbreak on record when 101,354 people were hospitalised. The Institute of Epidemiology, Disease Control and Research (IEDCR) confirmed 156 deaths from dengue last year.
Six people have reportedly died from dengue this year. The IEDCR, however, said just one patient died from dengue this year.