Before 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 seems to have decreased by at least 80 percent in most of the US  and at least 90 percent in most of Europe.
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 and at least 90 percent in most of Europe.