THE coronavirus R rate is above the crucial value of 1 across the UK, the country's top scientists say.

Four regions in England have seen a slight increase in the vital measure since last week – while every range is at or above 1.

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When the value is below one, it means transmission of the virus is no longer high.

But the reality is the true R rate probably lies somewhere between the upper and lower estimates.

Experts warn that as Covid cases are much lower than they were at the peak of the pandemic, the R rate is more sensitive to even small outbreaks.

The latest figures published today by the Scientific Advisory Group for Emergencies (SAGE) shows that the rate has increased across the country as a whole.

Regional breakdown

Last week, the UK's R rate was in a range between 0.8 to 1.0, but that's now up to 0.9 to 1.1.

The North West, South West, London and South East have also seen slight increases in their R rates.

In the North West, where a number of places have been forced into tougher restrictions, the R value range has increased from 0.8 – 1.1 last week to 0.9 – 1.1 today.

What does R Rate mean?

R0, or R nought, refers to the average number of people that one infected person can expect to pass the coronavirus on to.

Scientists use it to predict how far and how fast a disease will spread – and the number can also inform policy decisions about how to contain an outbreak.

For example, if a virus has an R0 of three, it means that every sick person will pass the disease on to three other people if no containment measures are introduced.

It's also worth pointing out that the R0 is a measure of how infectious a disease is, but not how deadly

London's range went up from 0.8 – 1.0 last week to 0.9 – 1.1 today, while the South West also went above the crucial value and is now at 0.8 – 1.1.

The South East's R rate range was just below 1 last week – at 0.8 – 0.9, but Sage say this has now nudged up to 0.8 – 1.0.

Growth rate

But Government advisers say that the latest 'growth rate' shows that the epidemic is somewhere between shrinking by three per cent and growing by one per cent every day. 

This measurement reflects how quickly the number of infections are changing day-by-day.

It is an approximation of the change of number of infections each day, according to Government experts.

If the growth rate is greater than zero (positive), then the disease will grow, but less than zero then the disease will shrink.

But the experts say that the figures lag a few weeks behind the country's current situation because the Government uses a variety of data sources.

A Sage spokesperson said: "We have been seeing indications that these values may be increasing, with estimated ranges increasing slightly from previous publications.

It is important to recognise that these are estimates, and there is a high degree of uncertainty with them

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

"It is also important to recognise that these are estimates, and there is a high degree of uncertainty with them. "

They added: "For this reason, Sage does not have confidence that R is currently below 1 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."

R rate accuracy

Meanwhile, experts have issued caution over the accuracy of the R rate estimate when cases are so few.

Prof Keith Neal said that local Covid clusters can also push the R rate up for an entire region when it may just be one small area.

The epidemiologist at the University of Nottingham said: “Making estimates of R with small number of cases becomes increasingly difficult and inaccurate.  Hence the wide range of the estimates."

Expected rise

Experts say that the rise in the R rate is to be expected as the country eases out of lockdown – and it may only go up further this winter.

Dr Michael Head, a senior researcher in global health at the University of Southampton, said: “We are seeing increases in new daily cases, and now we have an R number estimate that is approximately at the 1.0 threshold.

"The data suggests that as people mix more freely, there are probably increases in community transmission.

"This is to be expected, but highlights the problems in coming out of lockdown, particularly when there are many thousands of active cases in a population.

The 10 places on Covid watch list

The COVID Symptom Study app’s Watch List this week sees Blackpool, Halton and Manchester take the top three places with the rates roughly 10 times than the national average.

The list is based on the percentage of the population with symptomatic Covid-19 from data submitted by more than 3.9 million app users in the UK.

Here is this week's full list…

1. Blackpool – 0.4%
2. Halton – 0.35%
3. Manchester – 0.21%
4. Merthyr Tydfil – 0.21%
5. Kirklees – 0.2%
6. Rochdale – 0.19%
7. Dundee City – 0.18%
8. Nottingham – 0.17%
9. Blackburn with Darwen – 0.17%
10. Salford – 0.17%

These latest figures were based on the data from 8,798 swab tests done between August 2 to August 15.

"Suppressing COVID-19 is extremely difficult. We know that most cases are transmitted within the indoor environment.

"It’s currently August, and so outdoor meetings are possible, but as we head towards the winter, fewer people will be inclined to meet outside.

"That raises difficult questions about how best to handle social contacts across the winter months, particularly with the increased potential for transmission from younger populations, who usually have relatively mild cases, on to vulnerable populations where the consequences can be more serious.”

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