Mobility traces and spreading of COVID-19

Sebastian Alexander Muller; Michael Balmer; Andreas Neumann; Kai Nagel

• There is exponential growth of the number of infected persons initially. This also means that in the first approximately 10 days the number of infected persons is small, and the situation does not seem dramatic. This then rapidly changes, eventually leading to about 2.3 million simultaneously infected persons around day 44. Evidently, this is what we should not let happen; according to the above numbers it would imply 230,000 persons needing hospital care, many times more than what the system can absorb. 2 • The number of recovered persons goes up to about 97% of the population. 3 Once that many persons are immune, the reinfection rate drops below 1, and the virus dies out. • The model does not explicitly contain death cases. For the dynamics of the model, it is irrelevant if infected persons eventually recover or eventually die. Fig. 5 shows the share of infections occurring in different containers. The outcome shows that especially home, leisure, work and public transit activities have a high influence on the epidemic spreading. As the home activity cannot be reduced, the next sections will outline the effects of reducing leisure, work and public transport. One notices that about a fourth of infections occur in public transit vehicles. Our current assumption is that the contact intensity , as described earlier, is 10 times higher in public transport vehicles than in activities. Fig. 6 shows the effect a complete shutdown of public transport would have. The cases differ from each other with regard to the time point the measure is introduced. The maximum number of simultaneously infected persons goes down in every case, and the maximum is reached later compared to the base case. Also, the overall number of infected persons becomes smaller, implying a lower threshold of herd immunity. It becomes clear that shutting down public transport has an impact even when enforcing it as late as day 30.