A long way to go for dengue eradication

Climate change, multi-story buildings where cars are kept and washed and the huge number of under-construction buildings, and preserving water in drums or buckets are some of the main reasons for finding dengue cases around the year, said experts.

Although dengue was a disease associated with monsoon once, the incidence of dengue has been increasing year-round since 2014.

Since the official outbreak of dengue in Bangladesh in 2000, when 5,551 patients were hospitalised and 93 patients died, Directorate General of Health Services (DGHS) data indicate that dengue would typically begin to be diagnosed in June.

Prior to 2014, there were only five dengue cases diagnosed in May of 2001, one each in 2003, 2004, and 2009, and four in 2013 for the same month.

In April, only two dengue patients were hospitalised in 2003, one in 2004 and one in 2005. In March, only one patient was hospitalised in 2004 and one in January 2005. In 2014, however, these numbers were 15, 7, 2, 0, and 8 from January to May respectively.

 Since then, the monthly dengue cases have increased.

This year, the total number of cases is 3,210 (till yesterday), of which 2,022 were from January to May. The number of deaths is 24 so far, while 13 died between January and May, according to DGHS.

Entomologist Prof Kabirul Bashar of Jahangirnagar University, said due to the impact of climate change, Bangladesh's temperature remains favourable for the Aedes mosquito breeding all year round.

A temperature between 20 to 30 degrees Celsius is required for Aedes mosquito breeding.

"We get 20 degrees Celsius temperature even during winter; this is why we are getting dengue cases round the year," he said.

"The number of multi-story buildings and cars have increased significantly since 2014, both of which play a significant role in the spread of dengue during the dry season, as many people wash their vehicles in parking lots, where stagnant water accumulates," said Bashar.

To combat dengue, under-construction building owners must eliminate stagnant water in the basement. They need to use Novaluron pills or oil to preserve basement water.

He said certain areas of Dhaka have water shortages and store water in buckets or drums, contributing to year-round dengue outbreaks.

Bashar advised those who store water in drums or buckets to wash them weekly with detergent to prevent mosquitoes from breeding.

Entomologist GM Saifur Rahman of National University said the mosquito population has a general tendency to expand progressively.

"The lengthening of our rainy season as a result of global warming is an additional cause of year-round dengue transmission. Last year it rained until November, and this year it rained in January or February, so it wasn't dry for long," he said.

"Seventy to eighty percent of dengue patients are asymptomatic, which remains concealed because their symptoms cannot be observed. These patients are detectable via Sousveillance," he stated.

Laboratory-based active surveillance systems are required, but there are none in Bangladesh, said Saifur.

"If we had this system, we would be able to analyse their blood immediately after a fever and take effective control measures based on the results," he said.

"The government should at least implement laboratory-based active surveillance systems on a limited scale".

He added effective insecticide, surveillance system, and control measures are necessary to control Aedes mosquitoes properly.

In Kolkata they do their monitoring round the year which is absent in Bangladesh, he said.

"In our country, when a dengue case is discovered in a home, the city corporation's mosquito control team conducts a single anti-mosquito campaign. Eggs or larvae of Aedes mosquitoes must be constantly monitored for at least three months in areas where they are discovered. Since not all Aedes mosquito embryos hatch simultaneously," he added.