People with respiratory problems such as chronic obstructive pulmonary disease (COPD) and asthma are experiencing a flare-up of the conditions as a steady slide in mercury is matched by an unrelenting rise in air pollution.

In some cases the conditions are worsening to the extent that patients are being admitted to hospital, doctors said.

The difference between the day and night temperature is contributing to the spread of the diseases, the doctors said. Viruses become more active when temperatures fluctuate. Add to that the rise in air pollution, which is weakening the body’s natural defence.

“There has been a definite rise in the number of people with pre-existing respiratory diseases complaining of worsening symptoms. A few of them are being admitted to hospital,” said Chandramouli Bhattacharya, an infectious disease specialist at Peerless Hospital.

“Many of the patients with pre-existing respiratory diseases are experiencing breathing problems, which is why they are being advised hospital admission,” said Bhattacharya of Peerless Hospital.

Many people, especially younger ones, are suffering from allergic rhinitis, whose symptoms include runny nose and irritation in the throat or nose.

Bhattacharya said the results of most of the tests for influenza viruses are negative. “A host of other viruses could be at play,” he said.

Amitabha Saha, the director of critical care at Desun Hospital, said nearly 25 per cent of his patients are complaining of respiratory problems. It was about 5 per cent till 10 days or two weeks ago.

“Those with chronic cardiac failure or lower cardiac function, chronic asthma and chronic bronchitis are among the ones who are most vulnerable in this weather. The elderly and the children need to remain very careful,” Saha added.

Saturday’s maximum temperature was 24 degrees Celsius, three notches below normal. The minimum was 14, two degrees below normal.

A south Calcutta resident said she did not need any warm layer on Saturday afternoon. But when she was returning home in the evening, she had to wear a jacket. “The afternoons are still warm,” she said.

Geriatrician Dhires Chowdhury said many elderly people are suffering from respiratory tract infections, which are slowly progressing to the lower respiratory tract. “They are being advised hospital admission as it is difficult to manage the condition at home,” he said.

Winter is also the time when many go on vacation.

“Those with pre-existing conditions like COPD should avoid going to extreme altitudes. They should also avoid stepping out when the temperature is very low,” said Chowdhury.

“Also, they should avoid very long journeys. Take breaks in between. Carry a nebuliser and inhaler.”