Understanding the R Value and its 'expected' rise in the South West

You may hear over the next day or so that the R value in England has risen, including in the South West.

By way of context, the South West has the lowest number of cases across regions in England. Devon in particular has the fifth lowest number of recorded cases of all 150 upper tier local authorities.

This is what the Director of Public Health for Public Health Devon, Dr Virginia Pearson has said about the rise in R value, announced today.

"The R value is an important regional barometer based on modelling data, but while it provides an estimate of ongoing transmission, it alone cannot determine the rate of growth of coronavirus and does not accurately reflect Devon's local data on the ground. As such it should be treated with a little caution.

"The South West R value spans from Isles of Scilly to Bristol, and while there have been hotspots in other parts of the region that increase the R value, Devon's figures have remained low.

"We have the fifth lowest number of recorded cases when comparing Devon to all 150 upper tier local authorities and the consistency of the numbers suggest that levels have plateaued recently. That's in part due to our residents adhering to lock down, and heeding national guidance around staying home and social distancing. We have done well in that regard and need to keep that up.

"We continue to work closely with our Public Health and NHS colleagues to ensure the safety of our Devon residents, and we wait to hear the Government's response to this latest R rate announcement."

In addition, Dr Yvonne Doyle, Medical Director of Public Health England has said:

"Our estimates show that the regional R numbers have increased although they remain below 1 for most of England – this is to be expected as we gradually move out of lock down.

"It is vital that everyone continues with social distancing, practicing good hand hygiene and must remain at home and order a test if they have symptoms."

And Professor Debra Lapthorne, Regional Director PHE SW & Regional Director of Public Health NHS England South West, has said:

"The timing of the initial wave of infection was very different in each region, and consequently there will be some regional variation in R even now. Alongside the North West, and East of England, the South West had one of the lowest levels of activity prior to the lock down, due to a delayed spread into these regions.

"It is encouraging to see that the South West continues to see comparatively lower numbers of cases and deaths from COVID-19. We need to ensure all our communities continue to follow government guidance on social distancing and self-isolation. As lock down measures are eased across the country, it is vitally important we do everything we can to slow the spread of the virus and save lives."

"It's important to note that the R value should really be considered alongside incidence, and that a region may have a higher value of R, but a lower number of cases reported than another region with a lower value of R.

"The R value increase across England, and for the South West, is to be expected, given the relaxation from lock down and subsequent increase in contacts within the community. While the figure is helpful at a regional level, we advise treating any modelling data with caution."

Here is some information to help understand the R value.

The R number is only one component that determines the rate of growth of the epidemic, and does not say anything about the rate of occurrence of new infections, the prevalence of infection across communities and the current burden faced by the healthcare system. It should, therefore, not be used as the sole indicator of the current threat posed by an epidemic.