What is the R number? Why the UK's coronavirus reproduction rate is so important to plans to end lockdown

The higher the R value, the more infectious the virus. R3 means one person can pass Covid-19 to three people while R10 means it can be transmitted to 10. Dr Yuliya Kyrychko, a reader in mathematics at the University of Sussex, tells i: “The higher this number is, the more likely it is that an epidemic will develop, and as soon as it goes over one, that’s a clear sign that there will be an outbreak.