For the first time in the country's history, dengue cases outside Dhaka district have outnumbered cases inside the district, raising an alarm that the situation may worsen outside Dhaka.

Cases have now been reported in all 64 districts. Chattagram district came in second, after Dhaka, with 3,164 cases among the districts until yesterday morning.

Among others, 1,867 dengue patients were hospitalised in Chandpur, 1,743 in Laxmipur, 1,677 in Pirojpur and 1,426 in Barishal till yesterday morning.

Bangladesh witnessed the first dengue outbreak in Dhaka in 2000. Since then, the total number of cases in a particular year had never been higher outside Dhaka than inside.

Dhaka, however, has seen the highest 343 deaths out of the total 453 reported this year till yesterday.

According to the Directorate General of Health Services (DGHS), at least 1,565 dengue patients were hospitalised in 24 hours preceding yesterday morning, including 761 outside Dhaka.

The total number of cases went up to 95,877, including 48,944 outside Dhaka.

Experts have urged the government to pay the same attention to cities and towns outside Dhaka to control the spread of dengue.

Entomologist Kabirul Bashar of Jahangirnagar University said multiple reasons were behind the increase in the cases outside Dhaka.

As a huge number of residents of the capital have already developed antibodies to one or more serotypes of dengue virus, he said.

Though a total of 94,312 dengue cases have been reported till Thursday morning, the actual figure would be at least 10 lakh as only hospitalised patients are being tallied, Bashar told The Daily Star.

Also, the authorities outside Dhaka have not taken adequate measures to control the breeding of Aedes mosquito, he added.

Stressing the need for building awareness, the expert said no steps have been taken to make people outside Dhaka aware of Aedes mosquito.

Rain for longer period this year is another reason for the increase in Aedes mosquito population, he said.

Urbanisation outside Dhaka is also playing a significant role in the spread of dengue as Aedes mosquitoes are getting suitable atmosphere there to breed.

Bashar said it is very important to step up mosquito control measures in all cities to control the Aedes mosquitos, carriers of dengue virus.

The government will have to pay the same attention to every city for this purpose, he said.

GM Saifur Rahman, another entomologist, said there is a lack of necessary equipment to conduct anti-mosquito drives. The government should pay attention to this, he added.

"It would be much easier to control the spread of dengue and breeding of the mosquitoes if a vector management authority is set up. The authority would formulate proper guidelines in this regard," he said.

The LGRD ministry should send brief guidelines to the district authorities regarding the elimination of Aedes breeding grounds and personal protection, he observed.

Entomologist Manzur A Chowdhury said the infection rate outside Dhaka usually increases when patients from Dhaka travel outside.

"Earlier, the epicenter [of the viral disease] used to be Dhaka. The disease would spread outside if patients went out of the capital. But this year, the number of patients seemed to have simultaneously increased in and outside Dhaka due to the increased breeding of Aedes mosquitos."

Many people infected with the virus travelled outside the capital during Eid-ul-Azha holidays, which might have contributed to the spread of the disease, Manzur added.

He said it is now necessary to break the transmission chain.

"One of the main methods is to use mosquito nets while sleeping, wearing clothes covering exposed body parts, spraying repellants and ensuring cleaning of stagnant water and destroying all possible Aedes mosquito breeding sources," he added.