The ongoing intermittent rain, particularly in Dhaka, will worsen the dengue situation if the authorities fail to take the necessary steps to kill adult mosquitoes and destroy all breeding sources, entomologists said.

"As the Aedes population has already laid huge amounts of eggs in different containers, those will hatch thanks to this rainwater -- this new breeding generation will worsen the situation," said GM Saifur Rahman, assistant professor of medical and applied entomology at the National University.

Aedes mosquitoes lay eggs every three days and a female can produce 150 to 300 eggs in her lifespan. An egg can remain viable normally for around one year and it can hatch anytime in favourable water.

The authorities will have to kill all the adult mosquitoes and destroy all the possible breeding sources on an immediate basis to bring the situation under control, he said.

Light to moderate rain or thundershowers accompanied by temporary gusty wind are expected until 9:00 am in Rajshahi, Dhaka, Khulna, Barishal and Chattogram divisions, according to the Bangladesh Meteorological Department.

Many places in Rangpur, Mymensingh and Sylhet divisions can expect moderately heavy to very heavy rainfall.

The development comes at a time when the Directorate General of Health Services recorded another 12 deaths to take the body count from the mosquito-borne deadly disease to 273 this year.

Rahman suggested spraying BTI, a naturally occurring bacterium that kills mosquito larvae. When BTI, short for bacillus thuringiensis israelensis, is present in water, mosquito larvae feed on it and die -- long before they can grow up to become flying, biting, disease-spreading adults.

Dhaka North City Corporation has brought BTI, which would be applied for the first time in the country today.

"This is a good move but they are already late," said Manjur A Chowdhury, former chief executive officer of Safeway Pest Control.

The number of dengue cases was around 1,000 in May and it multiplied six times to around 6,000 in June.

In July, they multiplied more than seven times to 44,000, said Chowdhury, a former president of the Zoological Society of Bangladesh

"If the trend continues, the number could hit 2.50 lakhs in August. The two mayors of Dhaka and the ministry concerned are responsible for this situation as they never use the standard procedure for controlling Aedes mosquitoes."

The priority now should be on killing all adult mosquitoes instead of the larvae as a person becomes infected with dengue within seven days of the bite.

"But the city corporations are not doing this."

As per the World Health Organisation's recommendations, applying insecticide through the ULV machine is very important to get rid of this kind of epidemic-like situation.

Vehicle-mounted Ultra Low Volume (ULV) fogging machines are cold fogging machines that use large volumes of air at high pressures to transform the liquid into droplets that are dispersed into the atmosphere.

The government needs to purchase at least 10 ULV machines on an emergency basis, said Chowdhury, also the chairman of the Centre for Governance Studies.

After spraying through the ULV machine for 10 days, spraying and fogging through hand spray and fogger machines are needed once or twice a week.

"This will have to be continued until dengue cases stop," he said.

In the 24 hours to yesterday morning, 2,711 were hospitalised for dengue.

Alongside, the government needs to advise people to use mosquito nets while sleeping, wear full sleeve shirts and trousers and apply repellents to remain safe from this deadly virus, he added.