Bangladesh dengue outbreak continues as Aedes survives winter

Aedes mosquitoes will be in Bangladesh throughout the year, because the temperature they need will persist, experts say

A prolonged monsoon and rising temperatures were blamed for the worst outbreak of mosquito-borne dengue fever in Bangladesh last year, but the deadly disease has continued its bout even in mid-winter.

Experts say Bangladesh needs effective measures to fight Aedes aegypti mosquitoes, the known carrier of the virus, because climate change and other factors are helping the disease spread throughout the year.

Usually Aedes aegypti strike Bangladesh with dengue in the July-October period during monsoon when fresh water and warm weather create a suitable environment for the mosquitoes to breed.

But the mosquitoes have also been found in winter in the past few years.

In 2023, Bangladesh recorded 321,179 hospitalisations and 1,705 deaths from the viral disease, by far the highest figures.

The previous highest caseload was over 100,000 in 2019 and the death toll 281 in 2022.

In the first 11 days of 2024, Bangladesh registered 607 dengue cases and four deaths from the disease, up from 210 cases and one death in this period last year.

Most of the patients bdnews24.com talked to at several hospitals in Dhaka said their doctors advised admission because of a low platelet count in their blood, and other symptoms, such as vomiting, severe weakness and loose motion. Some of them were under intensive care.

AEDES SURVIVES WINTER

A routine survey by the Directorate General of Health Services under its Malaria and Vector-borne Disease Control Programme between Dec 8 and Dec 18 last year found Aedes larvae in 224 of 1,815 houses at 59 wards under Dhaka South City Corporation.

The percentage of such houses was 12.34 in the south . It was 11.62 percent in Dhaka North After the survey found Aedes mosquitoes in 155 of the 1,334 homes visited by the surveyors.

Mosquito density is chiefly measured using the BI, which counts the number of positive containers per 100 places inspected. BI exceeding 20 percent is risky, according to experts.

The survey put the index at a risky level at 35.6 of the houses in the capital.

Professor Kabirul Bashar, as mosquito expert at Jahangirnagar University’s zoology department.

Aedes mosquitoes will be in Bangladesh throughout the year, because the temperature they need will persist. If water is added to the condition, Aedes mosquitoes will breed.

Although it is winter and water is unlikely to gather somewhere like a bottle or scrapped tyres, Aedes found its way for breeding.

Prof Kabirul said the mosquitoes are mostly found in under-construction buildings, parking lots, where people wash cars, and water in pots thrown around a house.

“As Aedes mosquitoes can still be found, dengue will also be there, although fewer in numbers. We can’t free ourselves from dengue.”

Public health expert Dr Mushtuq Husain said mosquito attacks may ease in winter, but Aedes population will not become zero

“Because Aedes larvae cannot survive when the temperature is below 13 degrees Celsius. Temperatures in Bangladesh haven’t hit that level yet,” he explained.

And although there is no rain, water used by people accumulates in houses because of their unawareness, Dr Mushtuq said.

People also dump bottles and other sorts of containers here and there, he said.

“We’re making our environment dirty.”

He said the presence of dengue throughout the year will put the lives of the elderly with a weak immune system, pregnant women and children at risk.

He also fears that the number of dengue patients at high risk may be much higher than counted because many serotypes of the disease have been found in Bangladesh.