Hospital wards across the country are having to look after an unsafe number of patients, with hundreds of beds closed due to an outbreak of norovirus.
NHS England has said that on average almost 900 beds were closed each day during the week to Sunday 15 December.
Hospitals have reported fewer empty beds with bed-occupancy rates reaching as high as 95 per cent, 10 per cent higher than the recommended safe level.
As a result, fewer beds are available for sudden surges in demand or major incidents.
Meanwhile, the number of people arriving at A&E by ambulance is high, with almost 2,500 more people than in 2018, an increase of 2.6 per cent.
In total, 24 emergency departments were so busy that they temporarily closed to new admissions from ambulances.
The surge in demand comes as figures from Public Health England show cases of flu are continuing to rise higher than predicted levels, with more people in hospital than at the start of the month.
Siva Anandaciva, chief analyst at the King’s Fund think tank, said: "Despite a relatively mild start to the winter, the health service is running red-hot, with around 95 per cent of hospital beds occupied, well above the recommended safe level.
“This doesn’t bode well for the coming weeks when temperatures are likely to drop and flu levels increase.
“The government has promised more money for the NHS, but a credible plan to increase the workforce is also urgently needed. Even then, it will take time to stabilise services and patients will unfortunately continue to wait longer to receive the care that they need.”
A spokesperson for NHS England said: “Hospitals now have more beds open than this time last year, but flu and norovirus have kicked in a bit earlier so are adding pressure at a time when the NHS is already looking after significantly more people than ever before.
“The NHS has already looked after a million more people in A&E this year compared to last, and as we head into the holiday period it’s really important that the public help our hardworking staff by getting their flu vaccine now, using the free NHS 111 phone and online service for urgent medical needs, seeing their local pharmacist for minor ailments and ensuring they are stocked up on the medication they need.”
