Bill Harvey: Cool, cool people

Just as we have got our heads around the R number, now we must consider the K number.

The reproductive value, or R₀, is used to track how many people, on average, will be infected for every one person who has the disease. Lockdown and social distancing has helped maintain an R number to below 1.0. So, were R₀ be 0.8, for every 10 people with the disease a further eight would be infected – and the disease eventually dies out. Where R₀ rises above 1.0, the disease spreads. What is now known about the transmission of Covid-19 is that the likelihood of any individual infecting another varies significantly. This is termed overdispersion and is numerically represented by the value K, the overdispersion parameter.