  Non-pharmaceutical measures such as social distancing, can play an important
role to control an epidemic in the absence of vaccinations. In this paper, we
study the impact of social distancing on epidemics for which it is executable.
We use a mathematical model combining human mobility and disease spreading. For
the mobility dynamics, we design an agent based model consisting of pedestrian
dynamics with a novel type of force to resemble social distancing in crowded
sites. For the spreading dynamics, we consider the compartmental SIE dynamics
plus an indirect transmission with the footprints of the infectious pedestrians
being the contagion factor. We show that the increase in the intensity of
social distancing has a significant effect on the exposure risk. By classifying
the population into social distancing abiders and non-abiders, we conclude that
the practice of social distancing, even by a minority of potentially infectious
agents, results in a drastic change on the population exposure risk, but
reduces the effectiveness of the protocols when practiced by the rest of the
population. Furthermore, we observe that for contagions which the indirect
transmission is more significant, the effectiveness of social distancing would
be reduced. This study can provide a quantitative guideline for policy-making
on exposure risk reduction.
