The highly-infectious coronavirus mutation has created a "pandemic within a pandemic", experts have warned.
Striking a gloomy tone, Dr Adam Kucharski, an epidemiologist at the London School of Hygiene and Tropical Medicine, warned that this wave of cases was far worse than that during the first spike of March and April last year.
He also warned that the public aren't taking the virus as seriously as last year which, combined with the far greater transmission rate of the new variant, was creating a devastating mix.
Speaking on BBC Radio 4's Today, he said: "The early signals we're seeing are suggesting that there is probably less movement in the population than there was in November but perhaps slightly more than there was in April, and obviously that's concerning because, with this new variant, essentially each interaction we have has become riskier than it was before.
"Even if we went back to that last spring level of reduction in contacts, we couldn't be confident we would see the same effects as we saw last year because of the increased transmission.
"To some extent, we can think of this as a new pandemic within a pandemic," he explained.
"From the data coming out, this is a very serious threat and new data from Public Health England that came out on Friday suggested that risk per contact is probably 40-50% higher than it was.
"So both for the UK, and many other countries as well, we need to get away from this idea that we're going to see a repeat of what happened last spring with our behaviours and really face the possibility that this is much riskier and we're going to have to work much harder to reduce the impact."
It comes as experts warn London hospitals are just two weeks from being overwhelmed by Covid patients.
In a heartbreaking video, one NHS nurse said staff were forced to choose between dying Covid patients in crowded wards.
While another exhausted nurse claimed frontline healthcare workers are "so burnt out they can't eat".
On BBC Breakfast Saturday morning, one of Britain's top medical experts warned things are likely to get worse before they get better.
Dr Simon Walsh, deputy chair of the British Medical Association's consultants committee, said data from the last wave suggests the country is in for an extremely difficult few weeks.
"I'm afraid all of us who are working on the frontline believe, and this is based on the evidence I'm afraid, that it is going to get worse before it gets better," he said.
He also warned critical care was having to be spread "more and more thinly" due to surging cases, with as many as three patients per intensive care nurse.
The usual standard is one-to-one care.
Dr Walsh urged the government to both ramp up vaccinations and ensure the appropriate PPE is available for healthcare workers to make sure they can continue to go to work and don't get struck down by Covid.
He said: "They need to ensure that PPE supply is there when we need it because we were let down I'm afraid in the first wave by that and so our confidence needs to be restored by the government in vaccinating and ensuring that those PPE items are in place."