Ten times more people are in hospital with flu than this time last year, latest figures show.
There were an average of 344 patients a day with flu in hospital last week, compared with the 31 seen at the beginning of December last year, according to data released by NHS England.
It comes amid pressures on staffing too, with new figures showing nearly 360,000 NHS staff were absent from work last week through illness or self-isolating due to COVID.
Around 19 in 20 general and acute beds were taken up - 80% for adult critical care, NHS England's first weekly winter update also showed.
More than 13,000 (13,179) beds a day were taken up last week by patients who no longer needed one - this is up a quarter compared to the first week of December last year (10,510).
It follows a warning from NHS leaders that it is facing the threat of a "tripledemic" of COVID, flu and record demand on urgent and emergency services.
Sky News has been told there are concerns over the number of paediatric ICU beds available in some parts of the country.
The latest data shows last Thursday there were as few as 33 spare beds available in England - that's lower than at any point last winter.
While the exact figures might change slightly over the next two weeks, NHS England has confirmed there is higher PICU (paediatric intensive care unit) occupancy this month compared with previous years.
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The Paediatric Critical Care Society told Sky News: "Many PICUs are at, or over, their staffed bed capacity. This situation is likely to continue, or even worsen, over the coming months."
They said staff shortages, and an increasing number of complex patients are impacting capacity.
Some hospitals are operating on a one in one out policy with patients being moved to other trusts or being treated in the community to help alleviate the pressure, however, it said all children who need to be treated in hospital are receiving the appropriate treatment.
Camilla Kingdon, president of the Royal College of Paediatrics and Child Health, told Sky News: "We are concerned to hear reports of PICU bed shortages in parts of the country.
"We know paediatric teams are exceptionally busy this winter as a result of ever rising demand and staffing issues."
The Association of Ambulance Chief Executives (AACE) reported the highest ever monthly hours lost to ambulance handover delays.
There were 52,000 handover delays exceeding an hour in October, an increase of 7,000 from the previous month. Almost one in five of all handovers now exceeds 60 minutes and the overall amount of time lost has now doubled since October 2021.
AACE's managing director Martin Flaherty OBE said: "These crippling delays are a twin threat; they cause significant harm to patients who are forced to wait in the back of our ambulances, while our vehicles and crews are stuck and therefore unable to respond to patients who need us out in the community."
Professor Sir Stephen Powis, NHS national medical director, said the NHS is likely to experience its "most challenging winter ever" this year, adding the threat of a "tripledemic" is very real.
"It has never been more important to get protected against the viruses ahead of winter," he said.
NHS England launched its annual 111 campaign today - urging people to use its online service to reduce "record" demand on accident and emergency (A&E) departments.
People should still call 999 and go to A&E when someone is seriously ill or injured and their life is at risk, it said.