World Mosquito Day today: Lax monitoring led to surge in dengue cases

The absence of an effective mechanism to check Aedes mosquitoes, including proper and timely surveillance by the city corporations, is mainly to blame for dengue cases spiralling in the capital and elsewhere in the country, experts say.

They say hospitals are dealing with an increasing number of dengue patients every day and it has put an additional burden on the country's healthcare system already stretched by the Covid pandemic.

At least 32 dengue cases were reported in January, when the population of the Aedes mosquito -- vector for the dengue virus -- tends to be low.

But it was only in June that the two city corporations in Dhaka started mosquito fogging in areas where hospitalised dengue patients lived.  The city corporations took almost four months to swing into action after collecting patients' addresses from hospitals, the experts pointed out.

By that time, the number of dengue patients had already crossed the 250 mark, shows data from the Directorate General of Health Services (DGHS).

The situation has only worsened since then.

"To fight dengue, year-round surveillance on Aedes mosquitoes is very important," Saifur Rahman, an entomologist at the Bangladesh National University, told The Daily Star.

He said had the authorities conducted an extensive fogging in and around the patients' houses in January, the dengue situation would have been much better now.

On Tuesday, the country reported 329 dengue cases, the highest daily count this year.

In 24 hours till 8:00am yesterday, 270 dengue patients were admitted to hospitals across the country, shows DGHS data. Of them, 33 were admitted to hospitals outside Dhaka.

Another dengue patient died in those 24 hours, taking the official death toll to 31. All these patients died in July and August.

Till yesterday, the total number of reported dengue cases stood at 7,251, including 416 cases confirmed outside Dhaka, the data shows.

The mosquito-borne viral infection and Covid-19 present similar symptoms such as fever, headache and body ache, which makes diagnosis hard.

And most hospital beds, including those at the Intensive Care Units (ICUs), are occupied by Covid-19 patients, making it difficult for dengue patients to get hospital admissions, said experts.

Saifur went on to term the existing system for eradicating Aedes mosquitoes outdated.

Fogging, which is the government's preferred mode of controlling the Aedes mosquito population, is not good at nipping the nuisance in the bud, according to the entomologist, who did his PhD on medical entomology in Malaysia.

"It [fogging] is the last resort," he said, adding that the Insect Growth Regulators (IGRs) were very useful insecticides against mosquitoes.

The IGRs are insecticides that mimic hormones in young insects and can prevent reproduction, egg-hatching and moulting from one stage to the next.

"If we can use this kind of insecticides, we need not worry about the Aedes mosquito breeding like we are doing now."

Had those insecticides been available, people could have used them in places where water remained stagnant for a long time.

Saifur underscored the need for an integrated vector management unit, which is yet to be formed by the government.

Besides, he lamented that the two Dhaka city corporations lack entomologists, whose presence is crucial for monitoring the Aedes mosquitoes and advising anti-mosquito operations round the year.

The Dhaka North City Corporation (DNCC) has two entomologists, but the Dhaka South City Corporation (DSCC) does not have a single one.

The entomologist's post in the DSCC has remained vacant since last year, said an official of its health department, preferring not to be named.

"Serosurveillance is very important to know about the type of virus so that the authorities can take necessary measures accordingly," said Manzur Chowdhury, entomologist and former president of the Zoological Society of Bangladesh.

Serosurveillance is a globally used and trusted standard that measures the levels of antibodies against a certain infection and decodes the percentage of the population previously exposed to the virus. It is typically used as an extensive tool to see how far an infection has breached in a community.

The Institute of Epidemiology Disease Control and Research (IEDCR) has conducted serosurveillance in July and found serotype-3 active in Bangladesh this year like in 2019, when the country suffered its worst-ever dengue outbreak with more than one lakh dengue cases and 179 deaths.

The serotype-3 is the most dangerous variant among the four dengue serotypes, he said, adding that the IEDCR could have done it much earlier.

The two city corporations, however, beg to differ.

Contacted, Brig Gen Md Zobaidur Rahman, the chief health officer of DNCC, said they have increased the manpower and equipment to combat dengue after 2019.

An additional 540 workers were recruited after 2019 to take the workforce to about 1,000.

Apart from the anti-mosquito drive, the DNCC is working to build awareness among people since the beginning of the dengue season this year, Zobaidur said.

The insecticide DNCC is using is 100 percent effective in killing mosquitoes, he said, adding that they have tested it in three laboratories before using it.

"We examine every bit of the chemical to check its effectiveness."

Apart from having two permanent entomologists, the DNCC also has an advisory panel of entomologists.

The city corporation is fogging and larviciding at the dengue infected patients' houses and their surrounding areas since May.

Zobaidur, however, said there is a difference between theory and practice.

"Many things can be said theoretically but practically it is very difficult," he added.

The DSCC has also doubled its workforce and logistics accordingly.

"We have increased the workforce from five to almost 14 in each ward to conduct larviciding and adulticiding since 2019," said Abu Nasher, spokesperson for the DSCC.

Abu, however, said that they were facing difficulties in locating the patients' addresses provided by the DGHS.

"As many as 40 percent of the addresses of dengue patients that we received from the DGHS were wrong and now we are trying to collect those directly from the hospitals," he said.

Quizzed about the incorrect addresses, ABM Khurshid Alam, the director-general of the DGHS, said they provided the information to the city corporations after getting it from hospitals.

He said they would be more thorough going forward.