Impact of Social Reaction on the Dynamics of Epidemics

The effects of social reaction in an epidemic were investigated by means of in-silico experiments using the classical S(usceptible), I(nfected), R(emoved) mathematical model, but assuming a periodic function for the infection rate. This choice is known to be prone to counter-intuitive results: There is an increase in the total number of infected people over the course of the epidemic—the so-called final size of the epidemic. On further investigation, it was observed that this effect was associated with a decrease in the maximum number of infected individuals at any given time. For a disease that draw on resources of the public health sector, the latter behaviour is a desired one since it prevents the health system to succumb to an excess in diseased individuals due to the epidemic. Moreover, it was also noticed that the magnitude of both effects was seasonally dependent on the moment of the initial infection. Overall, these results suggest that modelling non-pharmaceutical interventions requires a more consistent linking between theory and epidemiological data.