Containment effort reduction and regrowth patterns of the Covid-19 spreading

In all Countries the political decisions aim at the Covid-19 spreading reduction and at reaching an almost stable configuration of coexistence with the disease, where a small number of new infected individuals per day is sustainable. In such a phase, the containment effort will be reduced in favor of a gradual reopening of the social life and of the various economical sectors and the evaluation of the possible infection regrowth should be very useful. Microscopic models, which take into account the details of the new social and economical conditions, would require a complex dynamics of the stakeholders. We discuss a less detailed approach which, on the basis of the collected data after few days from the beginning of the new phase, outlines different scenarios of the Covid-19 diffusion for longer time. The method applies a time dependent carrying capacity, analogously to many macroscopic growth laws in biology, economics and population dynamics. The illustrative cases of Singapore, Italy and Sicily are analyzed.