Coronavirus has changed everything. Make sense of it all with the Waugh Zone, our evening politics briefing. Sign up now.
The rate of spread of the coronavirus infection across the UK is shrinking, figures published by the government on Friday show.
For the UK as a whole, the current growth rate is minus 4% to minus 2% and the estimate of the reproduction number, referred to as R, remains at 0.7 to 0.9.
The growth rate reflects how quickly the number of infections are changing day by day.
If the growth rate is greater than zero then the disease will grow. If the growth rate is less than zero then the disease will shrink.
For example, a growth rate of plus 5% will grow faster than one with a growth rate of plus 1%.
It is different than the R rate, as R shows whether the epidemic is growing or shrinking – but not how fast.
It comes as the government lowered its coronavirus alert level from four to three – after the UK’s chief medical officers agreed the transmission of the illness is no longer considered to be “high or rising exponentially”.
Boris Johnson has said the alert level would be determined primarily, but not entirely, by the R rate.
Health secretary Matt Hancock said the move was a “big moment” for the UK, and showed the “government’s plan is working”.
Boris Johnson has previously said driving the R down is key to any further easing of the lockdown measures.
But his decision to lift some restrictions in England at the beginning of June caused some confusion as the Covid-19 alert level remained at four – which the government previously said would mean restrictions remaining in place.
It has five tiers from level one to five based on the spread of Covid-19 through the country.
At level five, transmission is high or rising and there is a risk healthcare services will be overwhelmed.
Level four means the epidemic is in general circulation and transmission is high or rising exponentially.
Level three is when the epidemic is in general circulation and gradual easing of restrictions can take place.
Level two is when the number of cases and transmission is low and “no or minimal” restrictions are required.
Level one means coronavirus is no longer known to be in the UK.
There is a time lag in the calculations, with the government scientists’ latest R value relating to what was happening two to three weeks ago.
If R is greater than 1 the epidemic is generally seen to be growing; if R is less than 1 the epidemic is shrinking.
R measures the number of people, on average, that each sick person will infect.
An R number of 1 means that on average every person who is infected will infect 1 other person, meaning the total number of new infections is stable.
If R is 2, on average, each infected person infects two more people.
If R is 0.5 then on average for every two infected people, there will be only one new infection.
At the start of March the World Health Organisation (WHO) estimated the R in the UK was between 2 and 2.5.
There are also thought to be significant regional variations in the spread of the virus.