A simplified drift-diffusion model for Pandemic Propagation*

We present a simplification of the susceptible-infected-recovery (SIR) and SIRS models for pandemic propagation that allows a quasi-analytical treatment of COVID-19 propagation across multiple countries. We discuss various sources of errors and uncertainty in the underlying parameters, ranging from complexity of interactions,  finite sample effects and reporting uncertainty. We show how we can interpret the evolution of the probability density function in terms of an overdamped classical particle diffusing in a tunable potential.