Before revision: Our compartment model shows that the COVID-19 case mortality rate  decreased by at least 80 percent in most of the US states and at least 90 percent in most European countries.
After revision: By fitting a compartment ODE model for Covid-19 propagation to cumulative case and death data for US states and European countries, we find that the case mortality rate decreased by at least 80 percent in most of the US states and at least 90 percent in most European countries.