Hospitals in England could be treating up to 20,000 coronavirus patients by December 31, dire projections show.
The Health Service Journal estimates that the number of Covid patients in hospital is rising by around 250 every day.
The publication has warned that on New Year's Eve, NHS England could be treating more people with Covid-19 than it did at the peak of the first coronavirus wave - when 18,974 patients were in hospital on April 12.
According to the estimates, the NHS could be "overwhelmed" in days as it is "on course to exceed the first wave in the next few days and, possibly, top 20,000 on New Year's Eve".
The projections come as a health chief warned struggling hospitals were "wall-to-wall" with coronavirus patients on Christmas Day as she issued a plea ahead of New Year's Day.
Dr Katherine Henderson, president of the Royal College of Emergency Medicine, said it is becoming increasingly difficult for doctors to manage coronavirus patients on hospital wards.
She issued a plea for people to follow the current restrictions, particularly at New Year's - when some may be tempted to meet their friends or family.
What do you think? Join the debate in the comments section below.
Dr Henderson told BBC Breakfast: "We see patients who are coming in who have Covid symptoms and then we have other people coming in with other symptoms who turn out to be Covid positive.
"Between that, there's a great deal of difficulty getting those patients through into the wards."
She added that the NHS will cope with the current spike in Covid-19 cases, but "at a cost".
Dr Henderson said: "The cost is not doing what we had hoped, which is being able to keep non-Covid activities going."
She said staff are "stretched" and, on top of that, a lot of people are off due to sickness.
She continued: "We will stretch, we will work double shifts, we will pull people in off annual leave, we will have all sorts of people working, so we will cope.
"But what you won't see is what is overwhelmed, which is the attempt to keep other services going and we just won't be able to do that, and people don't see that.
"It is always challenging in winter, nobody would say that it wasn't, but at the moment the level of patient need is incredibly high and other things stop being able to be done."
Dr Henderson said it is "incredibly important that we don't get another surge" which could put further pressure on the NHS.
Discussing New Year, she said: "Please, don't take a chance on this, please don't make it likely that we have an additional surge.
"Don't mix, wear masks, wash your hands, keep separate - all the things we know we really need people to take very, very seriously."
Professor Jackie Taylor, President of the Royal College of Physicians and Surgeons of Glasgow, said London and the South East are now experiencing what Scotland went through in the autumn.
She said: "Our busiest time in the second wave was in October and November, so the pressure that London and the South East is currently under we've already endured in October and November.
"We are still seeing significant amounts of patients with Covid and large amounts of standard respiratory infections and other emergency that we see at this time of year that mount up to a standard winter pressure."
She added non-urgent care will have to be paused in Scotland due to Covid-19.
Dr Taylor said: "Everybody has been working over the last nine months to try and ensure that we catch up with the backlog, and we will continue to do that.
"But the harsh reality is that some places that are under pressure, some of that non-urgent work will have to be paused, we have to focus on urgent work and we have to be able to roll out the vaccination programme."
She added: "There are hidden harms from Covid both in terms of operations and all sorts of other social and mental health and economic harms which we are all very, very aware of.
"As healthcare professionals, we want to be able to treat everyone, we want to ensure everyone gets the best of care, but unless we get a grip of Covid and really get on top of this then we won't be able to open up the other services again."
"We have to focus on getting on top of the acute problems we have at the moment."
