A new strain of the Delta Plus coronavirus variant is being probed in the UK amid fears it may be the fasting growing yet.
The UK Health Security Agency said on Friday it has designated a subvariant called AY.4.2 as a "Variant Under Investigation", saying there was some evidence that it could be more transmissible than Delta.
"The designation was made on the basis that this sub-lineage has become increasingly common in the UK in recent months, and there is some early evidence that it may have an increased growth rate in the UK compared to Delta," UKHSA said.
"While evidence is still emerging, so far it does not appear this variant causes more severe disease or renders the vaccines currently deployed any less effective."
It comes as government scientists have told Boris Johnson he needs to act now with Plan B measures if Britain wants to reverse surging Covid cases as we go into winter.
Advice to the Prime Minister and his Cabinet has been published in minutes of a meeting of the Scientific Advisory Group for Emergencies (Sage) on October 14.
Ministers were warned that “earlier intervention would reduce the need for more stringent, disruptive, and longer-lasting measures”.
Sage evidence showed that Government advice to work from home would be the most effective measure, compared with mask wearing and the introduction of Covid passports.
Despite rising Covid confirmed cases hitting 50,000 and expected to double in the coming weeks, ministers have refused to enact such Plan B measures instead insisting the pressure on the NHS is “sustainable”.
The Sage document stated: “Modelling suggests that the stringency of measures required to control transmission of a growing epidemic is increased by a faster doubling time.
“In the event of increasing case rates, earlier intervention would reduce the need for more stringent, disruptive, and longer-lasting measures.”
Figures released today also show one in every 55 people in England had Covid last week, a big jump compared to the week before.
The latest estimate from the Office for National Statistics warns that as many as 1,028,800 may have had coronavirus last week.
Two weeks ago one in 60 people in England were infected, meaning rates are rising rapidly.
At the peak of the second wave in early January, around one in 50 were estimated to have coronavirus.
The situation is even more stark in Wales, where 2.31% or one in every 43 people returned a positive test.
Northern Ireland and Scotland are doing much better, with 0.76% (one in 131) or 1.14% (one in 84) respectively.
The R number in England is as high as 1.2, meaning coronavirus cases in the country are growing.
England's COVID-19 weekly reproduction "R" number was estimated to have risen to between 1.0 and 1.2, the UK Health Security Agency said on Friday.
An R number between 1.0 and 1.2 means that for every 10 people infected, they will on average infect between 10 and 12 other people.
Last week R was estimated between 0.9 and 1.1.
The daily growth of infections was estimated between +1% and +3%, up from -1% and +2% the previous week.
