Multi-group SIS Epidemics with Simplicial and Higher-Order Interactions

TL;DR

This paper studies a multi-group SIS epidemic model on hypergraphs with higher-order interactions, revealing new bistability behavior and providing conditions for different epidemic outcomes.

Contribution

It formally establishes the presence of bistability in the multi-group simplicial SIS model and offers an algorithm for computing endemic equilibria.

Findings

Bistability appears in the multi-group simplicial SIS model.

Conditions for disease-free and endemic equilibria are derived.

Numerical analysis shows transition dynamics between states.

Abstract

This paper analyzes a Susceptible-Infected-Susceptible (SIS) model of epidemic propagation over hypergraphs and, motivated by an important special case, we refer to the model as to the simplicial SIS model. Classically, the multi-group SIS model has assumed pairwise interactions of contagion across groups and thus has been vastly studied in the literature. It is only recently that a renewed special attention has been drawn to the study of contagion dynamics over higher-order interactions and over more general graph structures, like simplexes. Previous work on mean-field approximation scalar models of the simplicial SIS model has indicated that a new dynamical behavior domain, compared to the classical SIS model, appears due to the newly introduced higher order interaction terms: both a disease-free equilibrium and an endemic equilibrium co-exist and are both locally asymptotically stable. This paper formally establishes that bistability (as a new epidemiological behavior) also appears in the multi-group simplicial SIS model. We give sufficient conditions over the model's parameters for the appearance of this and the other behavioral domains present in the classical multi-group SIS model. We additionally provide an algorithm to compute the value of the endemic equilibrium and report numerical analysis of the transition from the disease-free domain to the bistable domain.