Projecting the Spread of COVID19 for Germany

Jean Roch Donsimoni; Rene Glawion; Bodo Plachter; Klaus Waelde

The model predictions are very reasonable from a qualitative perspective. The larger the individual risk r to get sick, the higher the number N 2 (t) of simultaneously sick individuals and the later the peak t max of the epidemic. We also …nd, as was to be expected, that a larger r implies a longer duration of the epidemic. If we de…ne the end of the epidemic by the day t new 100 where only 100 new incidences are reported per day, we see that the end of the epidemic lies between 19 May and 25 June. Interestingly, the end of the epidemic is not monotonic in r: When the end of the epidemic is de…ned by the point in time t 1000 where 1000 sick individuals are left (N (t 1000 ) = 1000), the epidemic ends between 15 July and 27 September. Note that the t 1000 de…nition implies much later endpoints (of one and the same epidemic) than the t new 100 de…nition. Why are these numbers important from a public health perspective? The data section shows that Hubei and South Korea seem to have managed to keep the long-run ratio r from (12) at 1 in 1000 (Hubei) or 1 in 5000 (South Korea). If we believe that these values are long-run values, then either the individual probability r to get sick after infection of the long-run infection rate must be much lower than the standard values shown in 2 or sickness probabilities r must be lower.