Stochastic Time to Extinction of an SIQS Epidemic Model with Quiescence

Fuente: arXiv
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Auteurs principaux: Sanusi, Usman, John, Sona, Mueller, Johannes, Tellier, Aurélien
Format: Preprint
Publié: 2025
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author Sanusi, Usman
John, Sona
Mueller, Johannes
Tellier, Aurélien
author_facet Sanusi, Usman
John, Sona
Mueller, Johannes
Tellier, Aurélien
contents Parasite quiescence is the ability for the pathogen to be inactive, with respect to metabolism and infectiousness, for some amount of time and then become active (infectious) again. The population is thus composed of an inactive proportion, and an active part in which evolution and reproduction takes place. In this paper, we investigate the effect of parasite quiescence on the time to extinction of infectious disease epidemics. We build a Susceptible-Infected-Quiescent-Susceptible (SIQS) epidemiological model. Hereby, host individuals infected by a quiescent parasite strain cannot recover, but are not infectious. We particularly focus on stochastic effects. We show that the quiescent state does not affect the reproduction number, but for a wide range of parameters the model behaves as an SIS model at a slower time scale, given by the fraction of time infected individuals are within the I state (and not in the Q state). This finding, proven using a time scale argument and singular perturbation theory for Markov processes, is illustrated and validated by numerical experiments based on the quasi-steady state distribution. We find here that the result even holds without a distinct time scale separation. Our results highlight the influence of quiescence as a bet-hedging strategy against disease stochastic extinction, and are relevant for predicting infectious disease dynamics in small populations.
format Preprint
id arxiv_https___arxiv_org_abs_2503_06178
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Stochastic Time to Extinction of an SIQS Epidemic Model with Quiescence
Sanusi, Usman
John, Sona
Mueller, Johannes
Tellier, Aurélien
Populations and Evolution
Parasite quiescence is the ability for the pathogen to be inactive, with respect to metabolism and infectiousness, for some amount of time and then become active (infectious) again. The population is thus composed of an inactive proportion, and an active part in which evolution and reproduction takes place. In this paper, we investigate the effect of parasite quiescence on the time to extinction of infectious disease epidemics. We build a Susceptible-Infected-Quiescent-Susceptible (SIQS) epidemiological model. Hereby, host individuals infected by a quiescent parasite strain cannot recover, but are not infectious. We particularly focus on stochastic effects. We show that the quiescent state does not affect the reproduction number, but for a wide range of parameters the model behaves as an SIS model at a slower time scale, given by the fraction of time infected individuals are within the I state (and not in the Q state). This finding, proven using a time scale argument and singular perturbation theory for Markov processes, is illustrated and validated by numerical experiments based on the quasi-steady state distribution. We find here that the result even holds without a distinct time scale separation. Our results highlight the influence of quiescence as a bet-hedging strategy against disease stochastic extinction, and are relevant for predicting infectious disease dynamics in small populations.
title Stochastic Time to Extinction of an SIQS Epidemic Model with Quiescence
topic Populations and Evolution
url https://arxiv.org/abs/2503.06178