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Epidemiologist corrects Federal Councilor Berset: Cases are growing exponentially
After an interview in the “Sonntagszeitung”, there is a contradiction on the part of the Corona working group: even if the cases are now increasing slowly, the growth rate is doubling every four to six weeks.
Incorrectly communicated: Federal Councilor Alain Berset. Image: keystone
Those who always eat too much continually gain weight. Its weight increases linearly. Infectious diseases, on the other hand, always spread exponentially as soon as cases increase: instead of one or no other person, one sick person infects two new people, for example. If the circumstances remain the same, these two will in turn infect two, creating four new cases. These provide eight new cases and these eight (again two) for 16.
1-2-4-8-16-32? it’s the school’s well-known “power of two” factor. The exponential growth that quickly has strong effects. A classic illustration is a grain of rice on the first chessboard field; it would take a huge mountain of rice for the last field. Population growth is also exponential; a family tree illustrates this.
The measures are working: growth slower than in March
Now, the number of corona cases is not increasing very rapidly. They are currently doubling every four to six weeks. However, it is exponential growth, in contrast to the way Federal Councilor Alain Berset expressed it in the “Sonntagszeitung”.
Nicola Low, an epidemiologist at the University of Bern. zvg
He said, “I just find that we don’t have exponential growth right now. The number of cases is high, but it increases much more slowly than in spring. “
Nicola Low, an epidemiologist at the University of Bern and a member of the Corona working group on Twitter, corrected this: “The number of new cases of Covid19 is definitely increasing exponentially.”
Tanja Stadler, also a member of the task force, explains in more detail upon request:
Tanja Stadler, a mathematician at ETH Zurich. ETH Zurich
Even if growth is significantly slower than in March. It is enough that the famous R-value rises to just 0.1 above 1. It has been at 1.1 for a long time and represents slow exponential growth.
The number of weekly tests increased considerably during the summer, and therefore an explanation for the increasing number of cases could be the increase in tests. But 100 tests carried out today give more positive results than in June.
The so-called positivity rate has risen from around 0.4% in June to around 3% at the moment. Tanja Stadler says: “So the number of cases increases even after correction for more tests.” However, the curve will get steeper in the long run.
Spokesperson for the Federal Council: “The situation is not comparable to that of March”
Federal Council spokesman Peter Lauener said of Berset’s statement: “He was referring to the fact that there is currently no multiplication as extreme as in March. The current increase is not comparable to then. “
The fact that the epidemic is now spreading much more slowly than in March has to do with the fact that most of those infected do not infect other people because they follow hygiene and distance rules and wear more masks.
Contagious events are less common, as are the dreaded super-spreader events, where many other people suddenly become infected through closeness, bad air, and talking loudly.
