Fig. 7.

Estimation of the basic reproduction number${\mathbf{R}}_0$in Italy. The smoothed versions of the estimates of ${\text{R}}_0$ as a function of time t (days) are plotted for the three contagiousness scenarios: ${\text{R}}_0\left(t\right|0,7)$(a), ${\text{R}}_0\left(t\right|0,25)$(b), and ${\text{R}}_0\left(t\right|\mathrm{4,18})$ (c). We assumed as t = 0 the 22^nd of January 2020, typical assessment of the start date of the pandemic outbreak in Wuhan. The orange and violet rectangles highlight the time frames we used to simulate, within the SIR and A-SIR frameworks, the first (i.e., from 27^th of February 2020 up to 27^th of September 2020) and second wave (i.e., from 29^th of September 2020 up to 28^th of February 2021) in Italy. For each time frame, the maximum and the minimum value of the estimated ${\text{R}}_0$ were highlighted.