The government announced the measures yesterday afternoon amid fears a new Covid variant was “70 per cent more transmissible”.
How fast is coronavirus spreading across the country and what are the latest R Number estimates?
The R Number is the estimated number of people any given person who has the infection will pass it onto.
An R number between 1.1 and 1.2 means that, on average, every 10 people infected will infect between 11 and 12 other people.
A number above 1 means coronavirus is spreading exponentially within the population.
The current R value – the number of people an infected person will pass Covid on to – is now estimated to be between 1.1 and 1.2.
The UK estimates of R and growth rate are averages and should be regarded as a “guide to the general trend” rather than a description of the epidemic state.
These are the latest R and growth rate estimates by NHS England regions.
In England, Boris Johnson effectively cancelled Christmas for almost 18 million people in London, south-eastern and eastern England as the region was put into a new two-week lockdown from Sunday.
The Prime Minister said people should “lift a glass to those who aren’t there”, knowing that celebrating Christmas apart this year meant there would be “a better chance that they’ll be there next year”.
Under the new Tier 4 rules non-essential shops – as well as gyms, cinemas, casinos and hairdressers – have to stay shut and people are limited to meeting one other person from another household in an outdoor public space.
Those in Tier 4 were told they should not travel out of the region, while those outside were advised against visiting.
What is the R number?
The reproduction number is a way of rating coronavirus or any disease’s ability to spread.
It’s the number of people that one infected person will pass a virus on to, on average.
Measles has one of the highest numbers with an R number of 15 in populations without immunity.
That means, on average, one person will spread measles to 15 others.
Coronavirus (Covid-19) – known officially as Sars-CoV-2 – has a reproduction number of about three, but estimates vary.
How is R calculated?
You can’t capture the moment people are infected.
Instead, scientists work backwards.
Data – such as the number of people dying, admitted to hospital or testing positive for the virus – is used to estimate how easily the virus is spreading.
Why is a number above one dangerous?
If the reproduction number is higher than one, then the number of cases increases very fast – it snowballs like debt on an unpaid credit card.
But if the number is lower the disease will eventually stop spreading, as not enough new people are being infected to sustain the outbreak.