How is calculated the reproduction number R and where the pitfalls lie?

First of all the new infections and, later, the doubling time were it – and now the reproduction number R. alternate The key figures during the Covid-19 pandemic in the focus of the Public. The proclamation of new values is followed by Parts of the German population with almost as much excitement as the drawing of the Lotto numbers, or the publication of League results (in normal times) in the world of sports.

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Now, it is the reproduction number R: The value is one of the Central indicators for the evaluation of the gradient of a wave of Infection. R indicates how many people are infects a of Infected in a given period of time, on average. The lower R is, the better:

Is R 1, is an Infected on average less than other people – and the epidemic is running out.

Is R 1, the number of new infections is constant and linear. The curve does not rise so (more) exponentially.

Is R 1, is an Infected in the Mediterranean more than other people – the number of daily new infections will be greater. Angela Merkel has declared this at a press conference recently, very clearly:

How is calculated the reproduction number R?

The determination of the rate of reproduction is due to various factors and estimates complex. In addition, there are different calculation approaches:

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Both methods have a different focus: In the first case (RKI) deals with the Reporting and transmission of events, in the second (HIZ) to the suspected disease to happen. The crux of this is that – about at press conferences – the exact calculation methods and influencing factors are often barely communicates.

Where are the pitfalls in the calculation of the reproduction number R?

The Leibniz-Institute for economic research (RWI) indicates in his Newsletter “same UN statistics,” with a view on the Nowcast from the RKI to the fact, that the reproduction number is an estimate with a “not negligible estimation error”. This should be taken into account in the assessment of the current situation always. Therefore, self-reports, moreover, that R is increased to 1, may not be a cause for concern, as this increase might well vary within the estimation error, approximately between 0.8 and 1.1, such as the RKI, for instance, at 9. April stated.

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Furthermore, among other things, the number of Tests and detected infections has an influence on the reproduction number. Say: to Be carried out more Tests, recorded more infections. The number of unreported cases is small. “This will rise, in turn, the estimated R will tend, without, in reality, the course of Infection has changed,” writes the RWI.

Therefore, the Institute advises to interpret the reproduction number R in spite of their great importance for the evaluation of pandemic in history carefully.

What is the difference between R and R0 is?

In addition to the reproduction number R, especially at the beginning of the pandemic and more of the basic reproduction number R0 of the speech. Sometimes the values were incorrectly set equal.

The basic reproduction number, R0 , describes the “starting value” at the beginning of a pandemic, if it still does not give immunity to the entire population of an infection, so to speak, is exposed. According to RKI, R0 will be located in the Coronavirus according to various studies, between 2.4 and 3.3.

Change the value after taking measures, the effective reproduction number R of speech.

Sources: Agency, RKI, Leibniz-Institute for economic research (RWI),