Covid19 Case Numbers  Equation
The trend of the sum of all positively tested people over the days is comparable to the penetration of long rods as
a function of increasing impact velocity in armored steel:
The first part of the curve is exponential. After a point of inflection, the curve flattens and approaches a limit
value asymptotically.


y = cumulative total of cases x = days after first case

The parameters a, b and n can be fitted from the sums of all positively tested people over
the days. The condition is that the point of inflection has been passed.
The first derivative of the general
equation yields in case of covid19 to the sum of the daily cases and in case of long rods to the growth rate of
the penetration depth.


The fit values a, b and n can be used to predict the sum of all positively tested people
over the days as well as the daily cases.

Numerical examples are given in Case Numbers in Switzerland.
