Between Geography and Demography: Key Interdependencies and Exit Mechanisms for Covid-19

Antonio Scala; Andrea Flori; Alessandro Spelta; Emanuele Brugnoli; Matteo Cinelli; Walter Quattrociocchi; Fabio Pammolli

Another effect is represented by the impact of extreme quarantine measures on the post-lockdown time range. Indeed, increasing the strength α of the lockdown (i.e., reducing the social contacts) not only delays the time at which the lockdown can be lifted, but also induces a stronger reprise of the epidemic in the post-lockdown (see Sec. 8.2). Moreover, such approach could can result not sustainable for an economic system and motivate a gradual lifting of the lockdown measures to lessen the extant of further peaks. Furthermore, another counter-intuitive effect must be considered. Since to an attenuation α corresponds an effective reproduction number R eff 0 = αR 0 , at the critical value α crit = 1/R 0 the epidemic neither grows nor decreases. Thus, after t Lock the system stays stationary until the quarantine is released at t Unlock , and at this point the epidemic starts growing again as it was before the lockdown. In general, if α < α crit the system looks to ameliorate (infected, hospitalized, all the infective compartments go down) but as soon as the lockdown is lifted, the epidemic starts again to reach its full extent (see Sec. 8.2). Nevertheless, our estimate α ∼ 0.5 > α crit ∼ 0.3 for the Italian lockdown gives us hope that, perhaps, it will not be necessary to follow a repeated seek-and-release strategy in the post-lockdown phase. On the other hand, if a lockdown strength α ∼ α y, can be attained without disrupting the economy, the epidemic could be contained 8 . CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity.