R number

Why we should be wary of React’s R-number estimate

It seems that Boris Johnson will not begin to think about lifting lockdown restrictions until we have clear evidence that the latest wave of the virus has almost been defeated. So it was not exactly good news yesterday from Imperial College’s React Covid survey, which suggested that even though we are in lockdown, the R number is still almost at 1 in Britain – meaning the epidemic is barely shrinking. As part of React’s ‘viral opinion poll’ swabs were taken from over 160,000 people in England between 6 and 22 January. And while the researchers rowed back on a claim in their previous report that active infections could be rising

How worried should we be about a second wave?

Now that we are two months past the peak of the UK coronavirus epidemic, many fear the emergence of a second wave of the disease and remain anxious about any evidence that reopening the country has gone too far. For this reason media headlines like ‘Germany’s R number rockets again – from 1.79 to 2.88’ (Sky News) and ‘UK coronavirus cases no longer falling, ONS figures show’ (the Times) are amplified very quickly. But how worried should we really be by these headlines? By now, we have become familiar with the R number (the average number of people that each infected person will themselves infect) and are alert to the

Every part of England would pass Germany’s Covid test

As much as the government has any kind of strategy for lifting Britain out of lockdown it appears to revolve around the ‘R’ – or Reproduction – number. So long as this stays below one, we are told, the epidemic cannot progress – while the moment it strays above one then the disease will start to grow exponentially. That is easy enough to understand in itself. What is less easy to work out is just how this R number is calculated. We are told that for Britain as a whole it currently lies somewhere between 0.7 and 1. But whether this really means an awful lot is open to question.

Do the experts believe in the R number?

The R-number has been declared the most important metric in monitoring Covid in Britain. For young children to return to school in June, or for pubs to open in July, it is always linked to the rate of Covid transmissions – the R-number – staying below one. Above one is the danger zone: it means each infected person is infecting, on average, more than one other. So plans to liberalise are put on hold and we possibly enter a more severe lockdown once again. When explaining his strategy last weekend, the Prime Minister even showed a picture of an R-Number speedometer. But it gave no reading. We’re instead told a range: is that it

Is the R number a flawed measure?

Boris Johnson’s address on Sunday was always going to be challenging. The effects of Covid-19 – in terms of its horrific death toll and the drastic measures we’ve taken to prevent more loss of life – meant it was one the biggest and most important political statements in living memory. But what was also required was transparency and the explanation of very difficult scientific and medical concepts. In his statement, Boris Johnson drew attention to the R value, which he said was key to the changing lockdown measures over the coming weeks. If it crept above 1 this meant Covid-19 was spreading and the lockdown measures would remain in place, and