Northwick Park Hospital is experiencing "extremely high admission rates" for Covid-19, with surgeries postponed, except in emergencies.
Jon Baker, deputy medical director and head of A& E said the hospital in Watford Road has seen a surge in cases in recent days.
"It's safe and it's calm and controlled but it's extremely busy and we're back as we were with the first wave of patients. We've seen a real peak in the last few nights. Boxing Day was a challenge, a bit like New Year's Eve in terms of volume and sickness," he said.
"Normally we see people partying but it's been replaced by Covid."
He said it "feels more challenging this time" compared to the April peak as the hospital continues to maintain cancer services and some elective services.
The hospital has enough bed capacity, he said, but "finding staff to manage the beds is hard" and doctors have been redeployed from other areas which are not so busy.
However he said survival rates of Covid have "much improved".
"Our mortality rates at Northwick Park were always lower than other London and national average so we were always pretty good at managing Covid here and it was always like that throughout," he said.
"This shift time is a move towards non-invasive ventilation, using masks in the high-dependency area to avoid ITU, which is more effective for patients but requires a heavy oxygen requirement."
He stressed that people observe social distancing rules.
"There's a lot of social media people denying there's a problem in London but a few weeks ago we were seeing less than a hundred patients - but now it's a couple of hundred. It's really jumped up fast over two or three weeks," he said.
"If people don't keep social distancing and obeying the rules now the anxiety among us will become how many more patients can we manage?"
A North West London Hospital Trust spokesperson said: “In an emergency, you should continue to visit A&E, which is operating a two zone system so people with non-respiratory conditions are treated in a separate area.
"If you need help urgently but it isn’t an immediate emergency, please call 111, who can advise you and if necessary, even book you in for a timed slot at A&E.”
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