Coronavirus cases in hospitals outside current infection hotspots are going to get much worse, experts say.
Hospitals in the South East, London and South Wales have seen resources stretched to critical levels - with some patients even being triaged in ambulances outside.
Now, experts predict hospitals yet to experience the latest surge to prepare for it to "come their way".
Professor Andrew Goddard, President of the Royal College of Physicians, told the BBC: "All hospitals that haven't had the big pressures that they've had in the South East, and London and South Wales, should expect that it's going to come their way.
"This new variant is definitely more infectious and is spreading across the whole of the country. It seems very likely that we are going to see more and more cases, wherever people work in the UK, and we need to be prepared for that."
Medics have also warned of "unbearable" conditions in hospitals, with 23 hospital trusts across England now seeing more than a third of general and acute beds occupied by coronavirus patients.
One nurse who works at Whittington Hospital in north London said patients were being left in corridors and others spending hours in the back of an ambulance.
She said: "I'm worried about patient safety because if these little things are happening now when we're short and it's busy, it's only going to get worse.
"I don't know what else will happen - it worries me."
The number of Covid-19 patients in hospitals is at record levels in many areas of England - including London, the South West and the Midlands - with admissions rising above the levels seen during the first wave.
Staff in some hospitals are struggling to cope.
The nurse added: "It's not having enough nurses to care for patients, patient safety is being affected.
"Some are in corridors, being looked after in makeshift areas, makeshift wards have been created for Covid patients, and ICUs are running out of space.
"Staff have got low morale - we haven't even gotten over the first wave physically, emotionally and mentally, and now we're having to deal with this second wave."
The nurse called for a "complete lockdown" and said the public, who may not be adhering to restrictions as strictly as before, must stay home.
She said: "I don't necessarily blame the public when the messages have been so mixed from this Government.
"But I just want them to hear us and hear what we're saying because it's really unbearable."
A new study from Imperial College experts has also found the new mutant variant of coronavirus is “hugely” more infectious than the original strain.
Prof Jim Naismith of Oxford University said the findings indicated that even tougher lockdown restrictions would soon be needed.
“Unless we do something different the new virus strain is going to continue to spread, more infections, more hospitalisations and more deaths,” he warned.
Doctors’ leaders said NHS workers were at “battle stations” in their fight against the second wave and the coming weeks would be “nail-bitingly difficult” for the NHS.
They warned the public against “wilfully ignoring” social distancing and lockdown rules, without which the deadly disease would spread still faster.
There are also concerns that Nightingale Hospitals, which the Government spent £220m on setting up, would be useless because of staffing shortages.
Dr Alison Pittard, dean of the Faculty of Intensive Care Medicine, said she feared the impact of the second wave was now widespread in ICUs across the country.
“Everyone has seen what is happening in London and the pressure that is putting both on organisations and on staff as well, and we fear it is only a matter of time before it starts to spread to other parts of the country, and we are already starting to see that,” she said.
“It is really important that we try and stop the transmission in the community because that translates into hospital admissions.”