To want to tear my hair out when people talk about the ‘R number’ increasing - IT DOESN’T MEAN WHAT YOU THINK IT MEANS!

[GinFling]

I am SO sick of everyone having a hot take on this virus - from friends and colleagues, and especially the media. Article after article about how the R value is increasing, nearly over 1, etc etc, and how this means we are heading for a second wave/disaster/the sky falling in. No, it is more complex and nuanced than that, and in fact it’s harder and harder to have a low R as the virus gets less prevalent. It is also hugely skewed by local outbreaks - such as in care homes and hospitals.

These two articles are quite helpful in understanding it:
www.bbc.co.uk/news/amp/health-52944037
unherd.com/2020/05/what-the-headline-covid-figures-dont-tell-you/

I wish everyone would just STOP using R to pretend to know what they’re talking about. We’re not all statisticians or virologists, for good reason.

After one there is a growth in infections, and after two the growth is exponential.

@scaevola surely if the R rate is above 1 at all (even 1.1) there will be exponential growth? It would be an upward curve, not linear.

R0 is no better than guesswork. It is not real data.

I've found an article that explains it well. www.wired.co.uk/article/coronavirus-r-number-uk

If the R is higher than one then that means that a disease will keep on spreading to more and more people. Imagine that coronavirus had a R of two. That would mean that every person with the disease would go on to infect two new people. So if you started with 100 infected people, they would infect 200 people who would then go on to infect 400 people.

Even if the R was a lot lower – say 1.2 – the disease would still move through a population really quickly. Those 100 infected people would infect 120 people, who would then infect 144, then 173, then 208. In just four rounds of transmission, the number of people each time would double. Mathematicians call this phenomenon exponential growth, and it explains why coronavirus infected so many people all over the world so quickly.