In March 2020 the R rate was one of the big focusses of the pandemic.
Getting "the R" below one was the single biggest stated aim of policy makers in Wales and the wider UK (as well as flattening the curve).
However with cases dwindling in May and early June 2021 it had stopped being useful metric because just a handful of cases could wildly skew the data.
But with Wales heading into a third wave, with hundreds of new cases each day and the Delta variant spreading widely, the R number is worth paying attention to again.
What does the R rate mean?
The R number represents the amount of people each person with Covid-19 is infecting with the virus. So, for example the R rate for measles in population without immunity is 15. That means is one person has measles, they will infect, on average, 15 others.
With Covid, the benchmark has been to get the R number below 1. That's because if it goes above 1 the number of people becoming infected with the virus will grow exponentially. However, for as long as it remains below one the number of people infected with the virus will continue to fall.
How do Wales and England compare at the moment?
It depends whose estimates you look at.
The latest published data from the Welsh Government's Technical Advisory Cell, released on June 22, estimates the R rate in Wales to be between 1.1 and 1.4 . These are the figures that come from SAGE. However other figures from Public Health Wales, which have less lag time and uses case data only estimates with a high level of confidence that the R number is between 1.6 and 1.8 (up from 1.5-1.7 the previous week).
The doubling time for the whole of Wales is now 7.6 days meaning that in just over a week at this rate there will be twice as many cases.
At a regional level, PHW estimates by health board show the lowest R number is in Aneurin Bevan and Powys, both at 1.5 . The highest estimates are in Cwm Taf and Betsi Cadwaladr with an R of 2.1 and 2.4 . Numbers seen in Powys are low and so estimates should be treated with caution.
By comparison information from SAGE and the UK Government published on June 25 suggests the rate in England is between 1.2 and 1.4.
The break down of England looks like:
- East of England - 1.1 - 1.3
- London - 1.1 - 1.3
- Midlands - 1.2 - 1.4
- North east and Yorkshire - 1.2 - 1.5
- North west - 1.1 - 1.4
- South east - 1.1 - 1.3
- South west - 1.3 - 1.7
