  We introduce a theoretical framework that highlights the impact of physical
distancing variables such as human mobility and physical proximity on the
evolution of epidemics and, crucially, on the reproduction number. In
particular, in response to the coronavirus disease (CoViD-19) pandemic,
countries have introduced various levels of 'lockdown' to reduce the number of
new infections. Specifically we use a collisional approach to an infection-age
structured model described by a renewal equation for the time homogeneous
evolution of epidemics. As a result, we show how various contributions of the
lockdown policies, namely physical proximity and human mobility, reduce the
impact of SARS-CoV-2 and mitigate the risk of disease resurgence. We check our
theoretical framework using real-world data on physical distancing with two
different data repositories, obtaining consistent results. Finally, we propose
an equation for the effective reproduction number which takes into account
types of interactions among people, which may help policy makers to improve
remote-working organizational structure.
