The severity of dengue infection continues to be high even as winter is here, which is otherwise a lean season for the disease.

The authorities have yet to take necessary steps during lean periods (November-April), which are vital to controlling the spread of dengue in the following season, said experts.

Meanwhile, 3 dengue patients died while 971 others were hospitalised in the last 24 hours till yesterday morning, according to the Directorate General of Health Services.

The death toll thereby rose to 1,598, while the total number of cases rose to 3,08,167.

GM Saifur Rahman, assistant professor of medical and applied entomology at the National University, said the current weather conditions are still favourable for breeding of Aedes mosquitoes, the vector of dengue fever, as the temperature has not come down significantly yet and the country is still experiencing rain.

Mosquito control activities are not being done properly, which is one of the main causes of the persistent rise in the number of dengue cases this year, he said.

It is really tough to control Aedes mosquitoes once they spread everywhere, he also said.

If herd immunity is developed or if the temperature comes down to below 16 degrees Celsius, then the disease is likely to come under control naturally, Saifur said.

To contain the spread next year, the authorities concerned will have to chalk out a plan now and take necessary steps, he said.

"The absence of surveillance and initiating necessary steps outside Dhaka, especially in district towns, are causing higher infections this year," Saifur added.

Public health expert Mushtaq Hossain said failure in health management is also behind the huge number of deaths from dengue this year.

"The medical college hospitals are still overwhelmed with both critical and normal dengue patients. Many patients are being treated on floors. It becomes difficult for even highly skilled nurses and doctors to provide quality treatment in this situation," he said.

The number of deaths could be reduced if there were adequate facilities to provide treatment at primary healthcare centres, Mushtaq said.

He suggested equipping the rural primary health care centres with medical facilities for treating dengue patients.

HM Nazmul Ahsan, associate professor at Shaheed Suhrawardy Medical College Hospital, said the death rate this year was greater among high-risk group patients -- elderly, infants, obese, pregnant women, and patients with comorbidities like diabetes, high blood pressure, and complications of heart, kidney, lung, and liver.