The coronavirus infection rate is still too high. There will probably be a second wave | David Hunter

Test and tracing is launching today but, as the lockdown eases, it will need to be massively stepped up to have a significant impact

• David Hunter is professor of epidemiology at the University of Oxford

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We all now know the basics - the R is the average number of people someone infected with Covid-19 passes the virus on to. If it is greater than 1.0 the epidemic will grow exponentially. If it is less than 1.0 it will eventually disappear.

There are several types of R: the R0 that applies to a naive population with no immunity or interventions; and the effective R" or Re (also called Rt) that the politicians are talking about, and that measures how we are doing in controlling the virus.