Doctors are braced for a “difficult” Christmas and beyond as they treat a surging number of new Covid patients in hospital at the same time as more staff are absent because of the virus.

Medical staff at King’s College Hospital, in south-east London, have said they are holding out hope that they will avoid a huge surge of admissions before Christmas as Omicron spreads across the capital, but are feeling the pressure over staff shortages due to Covid-related absences.

The absences consist of staff who either tested positive or are isolating.

Professor Clive Kay, chief executive of King’s College Hospital NHS Foundation Trust, said just over 600 staff out of 14,000 are off sick due to Covid-related absences in the trust, which consists of King’s College Hospital, Princess Royal University Hospital in Bromley, Orpington Hospital, plus services at Beckenham Beacon and Queen Mary’s Hospital.

Nearly 170 coronavirus patients are currently being treated at King’s College and the Princess Royal Hospital as of Wednesday compared with 60 patients at the end of November.

A total of 102 patients are in general beds and 18 are in critical care at King’s, while 45 patients are in general and three patients are in critical care at the Princess Royal.

At its peak during the second wave in January 2021, the trust was treating 776 patients with Covid.

There’s lots of unknowns right now and that is generating quite a lot of anxiety because we are seeing such a massive rise in cases, all likely to the Omicron variant

Separate figures from NHS England show that 1,904 people were in hospital in London with Covid-19 as of December 21 – the highest number since March 2 and up 41% from a week earlier.

But it is far below the second wave peak, which saw 7,917 patients in hospital on January 18.

Dr Tom Best, 53, a consultant in the critical care unit at King’s College, said the unit has not seen a surge in coronavirus cases in critical care at the moment despite the huge surge in cases of Covid in the capital, but added the number of critical care patients tends to rise after a jump in hospital admissions.

He told the PA news agency: “Our actual coronavirus numbers at the moment in critical care have been fairly steady… there’s lots of unknowns right now and that is generating quite a lot of anxiety because we are seeing such a massive rise in cases, all likely (due) to the Omicron variant.

“So we are bracing ourselves for a significant impact. Adding to that is staff sickness, which is a reflection of the community prevalence we’re seeing at the moment.”

He said 20% to 25% of patients currently in critical care have Covid, while 5% of critical care staff – double the usual amount – are off sick with Covid-related absences.

“It presents extra challenges for the staff on the ground,” he said. “We have to ask staff to step up to cover shifts at short notice and that’s really challenging.

“Then there are times when there is a shortage, so staff on the ground have to work that extra bit harder to cover each other. We do our best to deal with it but there are significant challenges.”

Outlining the staff shortages, Professor Kay said: “I can’t pretend that the staff are happy with the situation. Last Christmas was ruined for so many staff and unfortunately, this wave is coming again over the Christmas period and that’s going to be difficult, but the staff are very professional.

“The staff here at King’s and indeed throughout the NHS and social care have done an amazing job over the last couple of years and will continue to do so.”

Dr Laura Jane Smith, 39, a respiratory consultant in one of King’s two Covid wards, said the shortages combined with the “relentless nature” of Covid is weighing on medics.

She told PA: “There are a number of different challenges we’re facing, one of which is staff shortages, and that’s been a real problem this week in particular.

“The other challenges are it continues to be really tough to be working in PPE all day. Communicating with really sick patients with the PPE on really does limit how well we can show how much we care and empathise with people going through a really difficult time with a severe illness.

“There’s lots to be hopeful for and things are certainly much better than they were last January.

“We have two wards of Covid patients currently in the hospital whereas in January we took over the entire hospital. That’s largely down to the vaccination programme and also the fact that things have moved forward so much with the drug treatments we now have.”

She added most patients being admitted to hospital with coronavirus are unvaccinated.

“A few have had one or several doses, and some of those will have other conditions that mean they’re at higher risk, but predominantly the patients that we’re seeing that are getting really sick still, needing advanced respiratory care and even intensive care, are patients who are not vaccinated.”

Professor Kay told PA the hospital is well-versed in treating patients with Covid but also planning for any surges.

“We are running the organisation in a very structured way, making decisions in a very clear, methodical and careful way and responding to the situation on a day by day basis,” he said.