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Latest estimates suggest the UK-wide reproduction rate of coronavirus – the so-called “R rate” – remains between 0.7 and 0.9, while across England it is 0.8-1.0.
The Scientific Advisory Group for Emergencies (Sage) also published regional values for R in England for the first time on Friday, with the South West having the highest range at 0.8 – 1.1.
The East of England is at 0.7 – 0.9, London, the Midlands, the North West and the South East at 0.8 – 1.0, and the North East and Yorkshire at 0.7 – 1.0.
But experts cautioned against the use of regional R values – the average number of people an infected to pass the disease on to – saying that as the number of infections falls, regional R values become less reliable.
Instead, from next week the government will publish the growth rates for regions that are based on data and make fewer assumptions.
Boris Johnson has previously said driving the R down is key to any further easing of the lockdown measures.
Sir Patrick Vallance, the government’s chief scientific adviser, this week said while the epidemic was “shrinking” it was not doing so “fast”.
He said the country would have to be “prepared to reverse things” if lifting elements of the lockdown led to a spike in infections.
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.