Explosive Transitions in Epidemic Dynamics

TL;DR

This paper explores how interventions in epidemic models can fundamentally change the nature of phase transitions, revealing three distinct types of explosive transitions influenced by intervention capacity limits.

Contribution

It uncovers three novel types of explosive phase transitions in epidemic dynamics caused by capacity-limited interventions, expanding understanding of epidemic control limitations.

Findings

Interventions can cause first-order discontinuous transitions.

Interventions can suppress large outbreaks exponentially.

Identification of a third, third-order continuous transition.

Abstract

Standard epidemic models exhibit one continuous, second order phase transition to macroscopic outbreaks. However, interventions to control outbreaks may fundamentally alter epidemic dynamics. Here we reveal how such interventions modify the type of phase transition. In particular, we uncover three distinct types of explosive phase transitions for epidemic dynamics with capacity-limited interventions. Depending on the capacity limit, interventions may (i) leave the standard second order phase transition unchanged but exponentially suppress the probability of large outbreaks, (ii) induce a first-order discontinuous transition to macroscopic outbreaks, or (iii) cause a secondary explosive yet continuous third-order transition. These insights highlight inherent limitations in predicting and containing epidemic outbreaks. More generally our study offers a cornerstone example of a third order explosive phase transition in complex systems.