Coronavirus: what the famous “R” parameter teaches us about the evolution of the epidemic

2020-05-17T18:20:03.673Z

DECRYPTION - The reproduction rate is a fundamental, but delayed, indicator of surveillance.The “natural” dynamics of the spread of a virus is quantified by the key parameter R0: it is the number of people infected, on average, by each infected patient in a normal situation. It is close to 3 for coronavirus (it is twice as much as influenza, but five times less than measles). When measures are taken to contain the epidemic, this figure is expected to decrease. It is then noted R: it is t...

The “natural” dynamics of the spread of a virus is quantified by the key parameter R0: it is the number of people infected, on average, by each infected patient in a normal situation. It is close to 3 for coronavirus (it is twice as much as influenza, but five times less than measles). When measures are taken to contain the epidemic, this figure is expected to decrease. It is then noted R: it is the effective reproduction rate of the virus. If it is greater than 1, the number of new cases increases every day: the dynamic is exponential, it's runaway. If it is equal to 1, the number of new cases is constant over time: the dynamics are linear, the epidemic under control. If it is less than 1, the number of new cases gradually decreases and the virus eventually disappears. R is therefore a key epidemiological surveillance parameter, widely used in Germany in particular, where we are worried as soon as it goes back above 1.

Read also: Coronavirus: do we really see the beginnings of a "second wave" in Germany?

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Source: lefigaro

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