Modelling daily infections with Covid-19 in Germany, France, and Sweden with a trend line based on day-to-day reproduction rates

Abstract

AbstractThe number of persons daily infected with Covid-19 as a function of time is fitted with a trend line based on an iterative power law (n = ¼) with a day-to-day reproduction rate modelled with a polyline. From the trend line, an effective reproduction rate Reff of Covid-19 is calculated. In all three states, Reff decreases in the initial phase to one indicating that there is no exponential growth. In Sweden, a steady state with Reff around 1 and a high daily infection rates. In Germany, Reff = 1 is reached before public and private life is restricted. With these restrictions, Reff is reduced further to 0.87 (CI95 [0.83.; 0.91]) after 40 days so that, speculatively estimated, 9500 premature fatalities within two months may have been avoided. In France, it seems that only strongly restricting private life sends Reff down to 1 and further down to about 0.7 (CI95 [0.3; 1.1]) after 45 days. With Reff permanently below 1, an exponential decline of the number of daily infections is observed in Germany and France.