Doctors said most of the extra patients during the winter surge were elderly people with heart and respiratory diseases and flu-like illnesses. Most of them needed care by medical departments.

On Monday, the average occupancy rate at all public medical departments reached 101 per cent. In November, it was 89 per cent.

The five busiest hospitals are Pok Oi Hospital, with a 130 per cent occupancy rate at its internal medicine department; Pamela Youde Nethersole Eastern Hospital (115 per cent), Prince of Wales Hospital (114 per cent), Tuen Mun Hospital (111 per cent) and Princess Margaret Hospital (106 per cent).

The authority's chief manager, Beatrice Cheng Shun-yan, said neither Pok Oi nor Prince of Wales hospitals were seriously overcrowded because they transferred the extra patients to other wards.

But the three other hospitals were packed and need to add temporary beds in the medical wards.

'The recent cold spell and flu peak seasons have added extra workloads to public hospitals and our frontline staff are all working very hard,' she said.

'We expect that the worst is yet to come. Traditionally, Chinese patients always avoid going to hospital during the Lunar New Year period. So many will rush to the emergency wards after the holiday.

'This year's holiday is very long and we expect the number of patients who turn up after the holiday will be quite high.'

Many employees will have a five-day holiday between January 24 and 28 - a weekend and a three-day public holiday.

Dr Cheng said busy hospitals had activated contingency plans, including suspending elective surgeries and paying extra allowances to medical staff for working longer hours or additional days. Other measures include enhancing community care and support to homes for the elderly so patients can be discharged earlier.

Hospital Authority figures show that the average daily attendance at the 15 public accident and emergency departments jumped from 5,401 in November to 5,553 for the week of January 4 to 10.

The daily average attendance at public accident and emergency wards ahead of Lunar New Year last year was more than 6,000.

David Hui Shu-cheong, an expert in respiratory medicine at Chinese University, said elderly people were at a high risk of getting flu or developing lung diseases or heart problems during cold weather.

Professor Hui said some patients needed longer hospital stays partly for social reasons. 'There are many single elderly patients at public hospitals and doctors cannot send them home because no one can take care of them,' he said.