Density dependence affects population recovery following an epidemic

Abstract

Current epidemiological models for the regulation of host populations by pathogens suggest that the reduction in the host population is largest shortly after the epidemic phase and that the host population partly recovers in the subsequent approach to endemicity. We find that this conventional view is not robust to a simple, biologically motivated addition: density-dependent population regulation (homeostasis). While rapid homeostasis typically enables a population rebound after the initial population suppression (the conventional view), we show that weak homeostasis can result in the opposite --- greater population suppression during the endemic phase compared to the initial epidemic. The effect of homeostasis, which is a property of the host population, can be substantial. This finding complicates the prediction of long term outcomes of population suppression by pathogens but not of short term outcomes.