More than a dozen flu patients were being treated by the Royal Surrey County Hospital last week, new figures show – as the NHS faces a "long and difficult winter".

The most recent NHS winter situation report shows an average of 14 flu patients were being treated by the Royal Surrey County Hospital NHS Foundation Trust each day in the week to December 14, with one in critical care.

It was up from 11 flu patients treated by the trust the week before.

Across England, an average of 3,140 flu patients were in hospital each day last week – up 18% from 2,660 the previous week.

The number stood at 2,629 patients at this point last year, including 14 at the Royal Surrey County Hospital.

NHS England said that there are "welcome signs" the rise in flu cases in hospital is slowing in some parts of the country – pointing out a fall in flu cases in hospitals in the North West over the past week.

Professor Meghana Pandit, NHS England's national medical director, said: "While some parts of the country will be breathing a sigh of relief with flu cases not rising as quickly as feared, we are nowhere near out of the woods yet.

"Combined with the impact of strikes, a stream of winter viruses means many hospitals will be on high alert in the days ahead.

"But it remains vital that people continue to come forward for NHS care as normal."

Health and Social Care Secretary Wes Streeting said: "Flu continues to put significant strain on the NHS, with record numbers of patients in hospital, and frontline services remaining under enormous pressure.

"The BMA's regrettable decision to pursue strike action at this critical moment is piling on the pressure, but the NHS team has responded brilliantly to keep the show on the road.

"Our entire focus is on keeping patients safe through the strikes and this peak period for the NHS."

Rory Deighton, acute and community care director at the NHS Confederation, said: "We are only in the early stages of what NHS leaders know is going to be a long and difficult winter.

"We do not yet know when or at what level flu will peak, and the impact of the current round of strikes on services could continue into the new year as appointments are rebooked and staff covering industrial action take time off."

Caroline Abrahams, charity director at Age UK, said: "The best Christmas present for many older people this year would be for the long-running dispute between the resident doctors and the Government to be finally over.

"We hope that everyone involved will redouble their efforts to reach a settlement, before any more damage is done to staff morale and camaraderie, NHS finances and, last but definitely not least, the quality and consistency of patient care."