South west R number and growth rate for new coronavirus cases

In today's update on the government website SAGE (the Scientific Advisory Group for Emergencies) estimates that the current rate of reproduction - known as the R number - in the south west now sit between 0.9 and 1.1, while the growth rate is estimated at between -2 per cent and +2 per cent.

Last week the growth rate for the region was estimated to be between -1 per cent and +2 per cent, meaning that while SAGE believes while the number of new infections could be rising by up to 2 per cent each day, it could also be shrinking by up to 2 per cent each day. This shows potential for faster rate of shrinkage that seven days ago, although still not as high as two weeks ago when figures showed potential for up to 5 per cent shrinkage.

The estimated growth rate reflects how quickly the number of infections changes day by day, as way of keeping track of the virus.

If the growth rate is greater than zero then the epidemic is growing. If the growth rate is less than zero then the epidemic is shrinking.

The size of the growth rate indicates the speed of change.

In real terms the number of new cases in Cornwall and the Isles of Scilly has been averaging at around three per day, although yesterday saw a jump of six new cases in the previous 24 hours.

Read next: Coronavirus in Cornwall round up - Thursday, August 27

All regions of the UK except the east of England show potential for growth this week, compared to last week when many showed a static growth rate or decrease. See the table below for this week's specific regional figures.

It should be noted that in the government figures the south west includes Cornwall and the Isles of Scilly, Devon, Dorset, Somerset, Wiltshire and Gloucestershire, with these weekly updates not breaking them down into counties.

SAGE also recognises there are limitations in both R number and growth rate, stating: "The growth rate is an average value that can vary. When case numbers are low, uncertainty increases.

"This could happen when only a very small proportion of people are infected, or the geographical area considered has a very small population."

This is particularly relevant to the south west.

It goes on to add that a higher percentage number "does not necessarily mean the epidemic is increasing in that region, just that the uncertainty means it cannot be ruled out."

Nationally the UK as whole has a growth rate of between -2 per cent and +1 per cent today.

The rate of infection is also thought to be increasing very slightly in the south west and in the UK as a whole.

In the south west it means that for every one person with the infection a further 0.9 to 1.1 people are likely to go on to be infected. Last week it was 0.8 to 1.1.

The values are shown as a range, with the most likely true values somewhere towards the middle of the range.

Nationally the UK's R number remains at 0.9 to 1.1, the same as last week.

The government website states: "The UK estimates of R and growth rate are averages over very different epidemiological situations and should be regarded as a guide to the general trend rather than a description of the epidemic state."

It goes on to add: "These estimates represent the transmission of Covid-19 from several weeks ago due to a time delay between someone being infected and needing healthcare.

"Estimates that use more timely data reflecting infections, suggest a higher R for England than shown here. As a result, SAGE does not have confidence that R is currently below 1 in England."

Region R Growth rate % per day

England 0.9-1.1 -2 to +1

East of England* 0.8-1.0 -3 to 0

London* 0.9-1.1 -2 to +1

Midlands* 0.8-1.1 -3 to +1

North East and Yorkshire* 0.8-1.0 -3 to +1

North West 0.9-1.1 -3 to +1

South East* 0.9-1.1 -2 to +1

South West* 0.9-1.1 -2 to +2

*Low numbers of deaths and/or a high degree of variability in transmission across the region means these estimates are insufficiently robust to inform policy decisions.