Daily Estimates for the Spread of COVID-19

A new website tracking the COVID-19 epidemic which is updated daily allows everyone to stay informed about the speed of epidemic spread in Germany and the rest of the world. To this end, scientists of Technische Universität Ilmenau cooperate with public health scientists of Universität Bielefeld to estimate the reproduction number, i.e. the mean number of people one infectious person will in turn infect. It allows to quantify the impact of the countermeasures that have been imposed, and also to continuously track the epidemic‘s progress over time. As such it is an important tool for policymakers.

Since the coronavirus has reached Europe, websites featuring charts which show the spread of the Coronavirus Disease 2019 (COVID-19) have attracted much public attention. In numerous articles data are analysed and interpreted. Now that countermeasures to slow the spread have been adopted in many countries, the pressing questions revolve around the efficiency of these measures. Even more importantly, when the countermeasures are to be loosened one has to ensure that the epidemic remains under control.

This is what the online tool developed by scientists around Prof. Thomas Hotz from the Institute for Mathematics at the Technische Universität Ilmenau accomplishes. Developed in close collaboration with Prof. Alexander Krämer from the School of Public Health at Bielefeld University, they created an interactive dashboard, which processes data from Johns Hopkins University for the entire world [1] and data provided by the Robert Koch-Institut for Germany as well as its federal states [2]. The analysis estimates the evolution of the reproduction number over time. “This number represents the average number of people one infectious person would infect if conditions remained the same”. explains Prof. Hotz. “A reproduction number larger than one means more people getting the disease than current cases, resulting in exponential growth; on the contrary, a value smaller than one indicates that the disease will eventually come to an end, at least as long as there are no new cases being imported from other countries. This number is therefore an appropriate measure for the speed with which the disease is currently spreading”.

The results clearly show the impact of the measures imposed by the German government (see figure): beginning with the closure of schools around March 16 the reproduction number has been declining, and with the stricter measures starting on March 23 this number has been approaching the critical value one. This means that no significant acceleration of the disease is to be expected given that the current mitigations stay in effect. “But what is going to happen, if we lift some of the restrictions?” wonders Prof. Krämer. “In this case we have to continuously track the development of the reproduction number - which is exactly what our tool enables us to”.

 

[1] English website: https://stochastik-tu-ilmenau.github.io/COVID-19/
[2] German website: https://stochastik-tu-ilmenau.github.io/COVID-19/germany

Contact:
Prof. Thomas Hotz                  
Institute for Mathematics              
Technische Universität Ilmenau           
Tel. +49 3677 69-3627               
E-Mail thomas.hotz@tu-ilmenau.de         

Prof. Alexander Krämer
School of Public Health
Bielefeld University
P.O. Box 100131, D-33501 Bielefeld, Germany
alexander.kraemer@uni-bielefeld.de