THE ‘R’ rate is a key metric that helps gauge the rate of the spread of Covid-19, helping the government make decisions on how to ease the lockdown.
The measure is often referred to in the coronavirus press briefings – here’s what it means and what the R rate is in the UK.
What is the R rate and how is it estimated?
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 inform policy decisions about how to contain an outbreak.
For example, if a virus has an R0 of three, it means that each sick person will pass the disease on to three more 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.
If the R rate of a disease is one or above, it will spread exponentially, infecting more and more people.
Therefore, being below R1 is key because it means the virus will likely peter out.
Scientists work backwards to estimate the R rate, as we can’t know the exact moment people are infected.
A range of data is used, such as ICU admissions, hospital admissions, deaths and positive tests.
It takes two to three weeks for changes in the R rate to be shown in this data, due to the time gap between infection and the need for treatment.
What does the R rate mean for coronavirus?
The World Health Organisation (WHO) estimated at the beginning of March that the coronavirus R rate stood between 2 and 2.5 – meaning the spread of the virus could snowball, with each infected person infecting between two and three others.
Thanks to the lockdown and the social distancing measures that have been in place, the UK is now below that.
In May, the R rate crept up, but it is thought that this is due to the outbreaks of the virus in care homes.
In comparison, the R rate of the seasonal flu is estimated to be roughly 1.3, while for the highly infectious measles it’s between 12 and 18.
Despite this, these figures are not set in stone because a given pathogen’s R value is constantly changing, as behaviour changes or immunity develops.
Jonathan Ball, professor of molecular virology at the University of Nottingham, told The Telegraph: “R0 is an indication of how much an infectious virus will spread in a population, and various things impact that value.
“The susceptibility, size and density of the population that the infection is introduced into matters, as well as the infectiousness of the virus itself.”
Predictions of the R0 for Covid-19 are currently varied because no one knows exactly how many people have been infected in total.
According to modelling published by Imperial College London, the R value stood somewhere between 3 and 4.6 in Europe before lockdowns came into effect.
What is the R rate in the UK?
We don’t know the exact R rate for the UK right now as it’s an estimate that’s constantly changing.
But as of Friday, May 29, the nation-wide R-rate is said to be between 0.7 and 0.9.
This means that every infected individual passes the disease to less than one other person.
This shows the lockdown has had a positive impact on the coronavirus pandemic as to bring an outbreak under control the R0 value needs to fall below one.
However, if the number rises higher than one, the epidemic will grow, which could lead policymakers to tighten lockdown restrictions.
Data released on May 14 from Cambridge University suggested that in the North East and Yorkshire the R rate – the average number of people an infected person can pass the virus on to – is feared to be at around 0.8.
On May 10, 2020, Boris Johnson urged the British public to help reduce the R value.
In his address to the nation, he said: “It depends on all of us – the entire country – to follow the advice, to observe social distancing, and to keep that R down.”
He added: “We must make sure that any measures we take do not force the reproduction rate of the disease – the R – back up over one, so that we have the kind of exponential growth we were facing a few weeks ago.
“And to chart our progress and to avoid going back to square one, we are establishing a new Covid Alert System run by a new Joint Biosecurity Centre.
“And that Covid Alert Level will be determined primarily by R and the number of coronavirus cases.”
He continued: “And in turn that Covid Alert Level will tell us how tough we have to be in our social distancing measures – the lower the level the fewer the measures.”
Sir Patrick admitted that the R0 value could be higher in some care homes and hospitals.
He said: “As I’ve said, it’s not true that the R is necessarily below one in every hospital or in every care home, and that’s the important area that we now need to look at and make sure that the appropriate measures are in place to try and reduce the R there.
“But it doesn’t change the overall view that I’ve described, that the R overall is below one and therefore we expect to see the slowing and the turn of the epidemic.”
What can reduce the R rate?
There are lots of infection control measures experts can use to push this number down and reduce the spread.
A study in the Lancet in April, for example, estimated that travel restrictions in Wuhan caused R0 to drop from 2.35 to 1.05 after just one week.
The social distancing measures introduced in the UK have had a substantial impact so far.
This is because as less people come into contact with one another, there is a lower chance for the virus to spread.
More generally, a vaccination would help reduce the R rate of any given disease as this would mean that one infected person wouldn’t be able to infect an individual who had been given a vaccination.
Did you miss our previous article…
https://covidnineteen.wiki/united-kingdom/breaking-joe-biden-pledges-police-reform-in-speech-that-sets-the-stage-for-the-us-election/