The Dhaka city corporations seem to have learned little from the past when it comes to controlling Aedes mosquitoes, as early measures were not taken to avert this year's deadly dengue outbreak, experts say.

According to the Directorate General of Health Services (DGHS), six people  died and 1,424 others were hospitalised in the 24 hours till yesterday morning. 

With the new numbers, 106 people have died in total, while the number of recorded dengue patients rose to 20,878 since the beginning of this year.

Different city hospitals are grappling with the influx of dengue patients.

With the viral disease yet to hit its peak, which normally takes place in August-September, entomologists and medical experts fear that the numbers of patients and deaths may cross those of 2019, when 1,01,354 people were infected and 179 died – the deadliest dengue year so far. 

Once a seasonal fever, dengue has turned into an all-year-long phenomenon since 2014, in the absence of necessary measures to control Aedes mosquitoes -- carrier of the dengue and chikungunya viruses -- during the November-March.

This is the period when mosquito distribution and breeding are low due to drier seasons.

Entomologist Manzur A Chowdhury said that inaction during this period has led to the disproportional rise in Aedes population this year.

"For the past 20 years, we see that activities to kill Aedes mosquitoes increase during the outbreaks, but all initiatives stop once the disease subsides," he told The Daily Star.

He also said that fogging and spraying is not enough to control Aedes and that the government needs an integrated vector management system in place. 

"The purpose of the system is to have round-the-year monitoring of Aedes and this needs sentinel surveillance."

He added that such surveillance allows one to know the exact locations of virus-carrying mosquitoes and act accordingly. 

"It also enables the authorities to make the people aware of those localities so that they can also play a vital role in eliminating Aedes breeding sources," said Manzur.

He further said the two city corporations should start anti-mosquito drives in January and continue the work till April to neutralise the Aedes clusters that remain active during that time.

"If they can do that, the disease will remain under control during the [monsoon] season [when Aedes is most active]." 

He also advised reviving a high-level committee that was formed by the Prime Minister's Office in 2019 to tackle the rise in dengue infections.

Entomologist GM Saifur Rahman, also a professor at National University, said the city corporations' casual approach early in the season played a vital role in the Aedes population's increase.

"When the population declined after October last year, no initiative was taken to kill off the rest, for which it has started spreading again. Then, we didn't try to detect virus-spreading mosquitoes at the beginning of the year."

Entomologist Kabirul Bashar, a professor at Jahangirnagar University, said the impact of climate change has also made Bangladesh dengue-prone throughout the year.

"A temperature between 20 to 30 degrees Celsius is required for Aedes mosquito breeding. We get 20 degrees even in winter …"

POLICY AWAITS NOD

Though the government initiated the formulation of a vector management policy in 2020, it is yet to see the light of day.

Contacted, LGRD Minister Md Tazul Islam said the policy has been prepared but is waiting for the Cabinet's approval.

Prof Bashar said, "A national vector control guideline and its proper implementation are necessary to control the Aedes population."

"The impact of climate change has also made Bangladesh dengue-prone throughout the year."

— Entomologist Kabirul Bashar

He added that a separate institute will be needed to conduct researches on all kinds of vectors and regularly share information with the agencies concerned in controlling Aedes.

"We have a national guideline in patient management, but we still don't have one to control Aedes," said Prof Saifur.

DENGUE DATA INADEQUATE

Though dengue patients are treated in different public and private hospitals, along with clinics, across the country, most of them are not centrally recorded, meaning the exact number of victims and their locations are not yet identified.

According to the DGHS, only 53 public and private hospitals in Dhaka and 72 district- and divisional-level hospitals are providing regular dengue-related data to the directorate.

However, there are 16,000 public and private hospitals, clinics, diagnostic centres and blood banks across the country. Of those, around 1,600 are in the capital.

"Due to a lack of adequate data, authorities concerned can't know the gravity of the situation," said entomologist Saifur. 

He suggested the government conduct serosurveillance tests – a blood test performed to detect the presence of antibodies – like it did during the Covid-19 pandemic, to identify asymptomatic dengue cases.  

"At least 70-80 percent dengue patients are believed to be asymptomatic,"

WHAT AUTHORITIES SAY

Brig Gen Md Zobaidur Rahman, the immediate past chief health officer of Dhaka North City Corporation, said they have been conducting anti-mosquito drives since the beginning of the year.

"The allegation that our efforts are lacking is not true."

He, however, said they were more focused on Culex mosquitoes from January and February, but made simultaneous efforts against Aedes and Culex in March and April and have been giving their full attention to Aedes since May.

About the unreported cases, LGRD Minister Tazul said there is no country who can report dengue cases without the hospital admission of patients.

Stressing the need for awareness, he said controlling Aedes needs public participation.

Dr Fazle Shamsul Kabir, chief health officer of Dhaka South City Corporation, in May said they have been conducting awareness campaigns in every ward since the beginning of this year and plan to extend those to educational institutions.

"We are also conducting our regular anti-mosquito drives."

Md Abu Nasher, public relations officer of DSCC, said they have been taking other steps as well, including holding advocacy meetings, conducting mobile court drives at different wards and anti-mosquito combing operations at different educational institutes.