Covid19 Case Numbers in Switzerland
At the beginning of April, reliable numbers of cases in Switzerland were available. My first attempt at a fitting resulted in an exceptionally good match between model and reality, which can be seen in the
following graph:

The fit values were as follows (period A): a = 46550 / b = 35.05 / n = 1.93 
The accordance between the number of cases and the model is surprisingly good. But from the beginning of April,
the number of cases was below the forecast of the model. The following measures ordered by the state had an effect:
At the beginning of March, events with more than 1,000 people were banned. Hygiene and behavioral rules (keep a distance
of 2 m, wash hands thoroughly, do not shake hands, etc.) were recommended. On March 13 the schools were closed and on
March 16 the state of emergency (lockdown) was declared for all of Switzerland. As a result of these measures, the
number of cases no longer rose and even fell from 23 March (point of inflection). This made it necessary to fit again for
the time later. With the number of cases from April 1 to May 4 (period B), the following fit values could be determined:
Period B : a = 31560 / b = 30.46 / n = 3.624
The following graphic shows the further course of the cumulative case numbers.


Period B could also be modeled very well. Even the extrapolation beyond May 4th to June 15th (42 days!) is perfectly consistent. The
following graph of the numbers of daily cases also shows this very impressively.


The next graphic shows an enlarged section to show the prediction phase more clearly.


With the end of the lockdown, the number of cases unfortunately increased again despite the prescribed behavioral measures: Initially moderate, but currently (October 9, 2020) exponential. The following graphic shows the course of the cumulative number of cases since the end of February, the time of the first Covid19 case in Switzerland.


Unfortunately, there is no end in sight to the exponential increase in the number of cases. A turning point in the course is also not evident. Further restrictions for the population have been announced.
Only when a turning point is clearly recognizable can the further course of the number of cases be estimated with the equation.

