Data-driven estimation of change points reveal correlation between face mask use and accelerated curtailing of the COVID-19 epidemic in Italy

Pedersen, M. G.; Meneghini, M.

Italy was the first Western country to be seriously affected by COVID-19, and the first to implement drastic measures, which have successfully curtailed the epidemic. To understand which contain measures effected disease dynamics, we estimate change points in COVID-19 dynamics by fitting a compartmental model to official Italian data. Our results indicate that lockdowns managed to cause the epidemic to peak in late March 2020. Surprisingly, we found a change point during the decay from the peak, which does not correspond to obvious drastic legal interventions, but may be explained by widespread promotion and mandatory use of face masks. We confirm these interpretations at regional levels, and find that the gradual reopening of society since early May has caused no change in disease dynamics. We speculate that widespread use of face masks and other protective means has contributed substantially to keeping the number of new Italian COVID-19 cases under control in spite of society turning towards a new normality.