Is the SARS-COV2 mortality rate coefficient decreasing over time?

The outbreak of novel SARS-COV2, which started in China late 2019, rapidly gained the pandemic status. Mathematical models are required to have good accuracy in predicting the outbreak evolution, to allow governments and local authorities to take actions aiming at minimizing the damage for the public health. In the current context, there are many uncertainties concerning the parameters entering the SIR model. Here we analyze the evolution of the death rate coefficient in Italy, USA, and Brazil. Experimental data support the conclusion that it is decreasing over time.