Collapse transition in epidemic spreading subject to detection with limited resources

TL;DR

This paper investigates how limited testing resources affect epidemic detection and control, revealing a second transition point where detection collapses and the disease spreads freely, informing resource allocation strategies.

Contribution

It introduces a modified compartmental model that incorporates resource constraints, identifying a second epidemic transition related to detection system collapse.

Findings

Detection system collapses at a critical reproduction number above 1.

A second transition point indicates the failure of detection under resource limits.

The model helps estimate necessary detection resources and confinement levels.

Abstract

Compartmental models are the most widely used framework for modeling infectious diseases. These models have been continuously refined to incorporate all the realistic mechanisms that can shape the course of an epidemic outbreak. Building on a compartmental model that accounts for early detection and isolation of infectious individuals through testing, in this article we focus on the viability of detection processes under limited availability of testing resources, and we study how the latter impacts on the detection rate. Our results show that, in addition to the well-known epidemic transition at ${\mathcal{R}}_0=1$, a second transition occurs at ${\mathcal{R}}^*_0>1$ pinpointing the collapse of the detection system and, as a consequence, the switch from a regime of mitigation to a regime in which the pathogen spreads freely. We characterize the epidemic phase diagram of the model as a function of the relevant control parameters: the basic reproduction number, the maximum detection capacity of the system, and the fraction of individuals in shelter. Our analysis thus provides a valuable tool for estimating the detection resources and the level of confinement needed to face epidemic outbreaks.