Doctors diagnosing patients at the public and private hospitals and private chambers attribute the sickness to seasonal weather change, which commonly causes viral and bacterial infections.

Respiratory (syncitial) viral infection is one of the very common complaints of sickness among the children. This infection triggers high fever with joint pain and inflammation of the lungs that also stimulates frequent difficult coughs.

"Hundreds of patients, many of them elderly people, turned up in the last three weeks. They had breathing difficulties and frequent coughs that are common symptoms of respiratory viral infection," said a senior physician of Shaheed Suhrawardi Hospital.

"Immune or defence mechanism of the body becomes weaker due to viral infection that also allows invasion by bacteria. We call it secondary bacterial infection that often turns grave if not diagnosed early," said Prof Khan Abul Kalam Azad of Shaheed Ziaur Rahman Medical College Hospital in Bogra.

Pneumonia, which results from infection of the air passages in lungs and is closely linked to ARI, is also affecting people at an alarming rate. Hundreds of children suffering from pneumonia have already been hospitalised. The situation has turned quite serious in the last two weeks.

Pneumonia makes properly breathing difficult for the patients, who often require artificial mechanism of ventilation to enable breathing. If not treated, the disease may cause death within three to four days. It attacks mostly children under five, but adults may also suffer if they do not protect themselves from cold.

At least 100 cases of pneumonia were diagnosed in September and early October at the country's biggest children's hospital -- Dhaka Shishu Hospital.

"There's no denying the fact that there is a rush of pneumonia patients before the onset of winter every year. But we can't accommodate all of them. In such a situation we can neither refuse nor accept them for admission," said a consultant of Dhaka Shishu Hospital.

At Nibedita Clinic, Dr Salauddin Hospital, Ma-O-Shishu Hospital, paediatric departments at Dhaka Medical College Hospital, Bangabandhu Sheikh Mujib Medical University Hospital and the childcare hospital over 300 patients, mostly infants, were diagnosed for pneumonia in the last two weeks.

The figure of admission this time from the disease was less than half last year.