Hospitals are seeing a "real rise in pressure" as the number of coronavirus patients receiving treatment is heading towards the April peak.
Paramedics in the capital are receiving almost 8,000 call-outs a day and Boxing Day was described as one of the London Ambulance Service’s “busiest ever days” amid warnings ambulance trusts are under “extreme pressure.”
It comes as Cardiff and Vale University Health Board put out a plea on social media on Saturday calling for assistance from medical students after a surge in Covid-19 cases.
Politicians and medical experts pointed to the plea as a sign NHS services in Wales are buckling under the strain of escalating infection rates.
Saffron Cordery, deputy chief executive of NHS Providers, told the BBC: "We're seeing a real rise in the pressure for hospital services, but also other types of NHS services as well... ambulance trusts in particular are coming under extreme pressure, as are community and mental health services".
Pointing towards issues in London and the South, Ms Cordery added: "Part of the issue is many more people coming through the door with Covid, but also people coming through the door with other conditions as well."
The 7,918 calls received by London Ambulance Service (LAS) on December 26 was up more than 2,500 on the 5,217 received on the same day last year, and medics are receiving support from other ambulance services in the South.
LAS said in a statement: "Like NHS organisations across the country, demand for our services has risen sharply over the past weeks and we are now taking up to 8,000 999 calls a day compared to 5,500 on a typical 'busy' day.
"Our colleagues in emergency departments are also under pressure receiving our patients as quickly as they can.
"We are working urgently with NHS partners to reduce any delays."
Reports of pressures the NHS is facing come as hopes grow for the approval of the Oxford/AstraZeneca vaccine in the coming days, with volunteers ready to help roll out the jab nationwide, according to reports.
AstraZeneca chief Pascal Soriot has said researchers have found a “winning formula” with their two-dose system.
Professor Sir John Bell, an Oxford academic and member of the government’s Scientific Advisory Group for Emergencies, said he expects the vaccine to be approved by the MHRA "pretty shortly.
As vast swatches of the country enjoy the festive break under harsh tier 4 restrictions, the question of schools reopening in January is “very finely balanced” according to Sir Jeremy Farrar, a member of the Government's Scientific Advisory Group for Emergencies.
He said:"I think the next few weeks going into January are going to be extremely difficult across the whole country."
Sir Jeremy, director of the Wellcome Trust, told the BBC Radio 4 Today programme. "Certainly my own view is that schools opening is an absolute priority.
But society - and eventually this is a political decision - will have to balance keeping schools open, if that is possible, with therefore closing down other parts of society.
"It is going be a trade-off between one or other. You cannot have everything. You cannot have the whole of society opening, and schools opening and further education and universities, and keep R below 1 with this variant.
"I think there are some very, very tough choices. We are going to see these continued pressures at least over the next two or three months."
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