By December, it had become the "dominant variant" in London.
A new coronavirus strain has gripped England that spreads faster and thus requires greater public vigilance, confirmed the country's chief medical officer Chris Whitty on Saturday.
A summary of the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) meeting said: "Studies of correlation between R-values and detection of the variant: which suggest an absolute increase in the R-value of between 0.39 to 0.93". He tweeted: "The new strain of COVID-19 is worrying & real cause for concern & extra caution".
- Is this something to worry about? Belgium followed suit, saying it will stop air connections to the United Kingdom for 24 hours on Monday (December 21).
What is the new strain of Coronavirus?
"We are, of course. looking very carefully into this", US Covid-19 vaccine program head Dr. Moncef Slaoui told CNN's State of the Union programme. Although there is considerable uncertainty, it may be up to 70% more transmissible than the old variant. But he said that "urgent work" was underway to confirm this.
- Is it the first novel strain detected in the UK?
However, Sir Patrick said there was "no evidence" the variant caused more severe disease or increased the risk of being admitted to hospital.
But it's thought this is the first strain that will be investigated in such detail by PHE.
"Currently nothing to suggest that this variant is more likely to cause serious disease".
Let's address what we do know.
"The only way you can do that is by restricting social contacts and essentially, especially in Tier 4 areas, everybody needs to behave as if they may well have the virus and that is the way that we can get it under control and keep people safe", he added.
Certain countries that had been model managers of the pandemic such as Germany and South Korea find themselves facing more challenging circumstances. Household mixing will be banned in London and southeast England, and socializing will be restricted to just Christmas Day across the rest of England.
The new variant may also raise questions about treatments and herd immunity even as remarkable progress is made on vaccines. This does not necessarily mean it is more unsafe or will result in more deaths.
Mr Hancock said such behaviour was "totally irresponsible" while Transport Secretary Grant Shapps said additional police were being deployed to ensure that only people who needed to travel did so.
The vaccine produces antibodies against many regions in the spike protein, and it's unlikely a single change would make the vaccine less effective.