The latest coronavirus R number and virus growth rate in UK - what it means

[Cookham v Coronavirus]

The coronavirus R number and the virus growth rate in the UK may be increasing, government scientists have said - though the official figure has remained the same.

The R number represents the number of people each Covid-19 positive person goes on to infect.


Data released on Friday by the Government Office for Science and the Scientific Advisory Group for Emergencies (Sage) shows the estimate for R across the UK is between 0.9 and 1.1.

The growth rate of coronavirus transmission, which reflects how quickly the number of infections is changing day by day, has changed slightly.

The official figure in England remained the same as last week - between 0.9 and 1.1.

And the growth rate for the whole UK is now between -2 per cent to +1 per cent - which means the number of new infections is somewhere between growing by 1 per cent or shrinking by 2 per cent every day.

That's an increase from the previous estimate published last week, which was between -3 per cent and +1 per cent. The most likely value is towards the middle of the range, experts say.

Recent changes in transmission are not yet fully reflected in the estimates because the data used to calculate R and growth rate reflect the situation from a few weeks ago.

Epidemiological data, such as hospital admissions, ICU admissions and deaths, usually take two to three weeks to reflect changes in the spread of disease.

This is because of the time delay between initial infection and the need for hospital care. Therefore, the figures published on Friday more accurately represent the average situation over the past few weeks rather than the current situation.

But models that use Covid-19 testing data, which have less of a time delay, indicate higher values for R in England, the Government Office for Science statement said.

It added: “For this reason, Sage does not have confidence that R is currently below 1.0 in England. We would expect to see this change in transmission reflected in the R and growth rate published over the next few weeks as we gain more certainty of what is currently happening.”

The statement added: "Estimates of R and growth rate per day are less reliable and less useful in determining the state of the epidemic when disease incidence or the number of deaths is low, or where there is significant variability in the population or incidence, for example during local outbreaks.

"When this is the case, estimates of R and growth rate should not be treated as robust enough to inform policy decisions alone.

"Both are average measures and will smooth over localised outbreaks or over short periods of time, which will not accurately reflect the way infections are changing throughout the region."