The reproduction rate of the coronavirus in England could be higher than 1, according to a leaked document from Public Health England.
Keeping the rate below 1 has been considered key to easing lockdown because it means the virus is shrinking as not everyone who catches it passes it on.
If the figure rises higher, it means people infected with the virus are passing it on to others at a rate faster than one-to-one, and the outbreak will grow as a result.
A document from Public Health England, seen by the HuffPost, showed PHE admitted there is ‘uncertainty’ about the number, which is always an estimate and not actually measurable.
Officials have said for weeks that the R of the UK as a whole is between 0.7 – 0.9, rising to as high as 1.0 in London, the Midlands and the North West, according to data last week.
But PHE is not even sure these are correct, according to the document, which was sent out to doctors around the country.
It said: ‘There is uncertainty around these and thus we cannot preclude R being above 1. For the North West and South West, we estimate R to be around 1.’
If the R rate rises above one Britain’s outbreak will start to grow again. A rate of 0.5, for example, would mean every 10 infected people pass it on to only five others, while a rate of 1.2 would see them give it to 12
A Government spokesperson said the document, dated last Thursday before the most recent official announcement, does not change the latest estimate of R.
They said: ‘SAGE was totally clear when the most recent UK R rate was released last Friday that it stood at 0.7-0.9. The rate for England was also 0.7-0.9.
‘The latest ONS [Office for National Statistics] figures also show that the number of infections is declining.
‘Most significantly, the “growth rate” for England alone is at -4 to -1. That means the number of infections is declining daily by between 4 and 1 per cent.
‘All of these figures were signed off by SAGE, on which PHE representatives sit.’