Oscillation in the SIRS model

Fuente: arXiv
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Autores principales: Marenduzzo, D., Brown, A. T., Miller, C., Ackland, G. J.
Formato: Preprint
Publicado: 2025
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author Marenduzzo, D.
Brown, A. T.
Miller, C.
Ackland, G. J.
author_facet Marenduzzo, D.
Brown, A. T.
Miller, C.
Ackland, G. J.
contents We study the SIRS epidemic model, both analytically and on a square lattice. The analytic model has two stable solutions, post outbreak/epidemic (no infected, $I=0$) and the endemic state (constant number of infected: $I>0$). When the model is implemented with noise, or on a lattice, a third state is possible, featuring regular oscillations. This is understood as a cycle of boom and bust, where an epidemic sweeps through, and dies out leaving a small number of isolated infecteds. As immunity wanes, herd immunity is lost throughout the population and the epidemic repeats. The key result is that the oscillation is an intrinsic feature of the system itself, not driven by external factors such as seasonality or behavioural changes. The model shows that non-seasonal oscillations, such as those observed for the omicron COVID variant, need no additional explanation such as the appearance of more infectious variants at regular intervals or coupling to behaviour. We infer that the loss of immunity to the SARS-CoV-2 virus occurs on a timescale of about ten weeks.
format Preprint
id arxiv_https___arxiv_org_abs_2504_00670
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Oscillation in the SIRS model
Marenduzzo, D.
Brown, A. T.
Miller, C.
Ackland, G. J.
Biological Physics
Populations and Evolution
We study the SIRS epidemic model, both analytically and on a square lattice. The analytic model has two stable solutions, post outbreak/epidemic (no infected, $I=0$) and the endemic state (constant number of infected: $I>0$). When the model is implemented with noise, or on a lattice, a third state is possible, featuring regular oscillations. This is understood as a cycle of boom and bust, where an epidemic sweeps through, and dies out leaving a small number of isolated infecteds. As immunity wanes, herd immunity is lost throughout the population and the epidemic repeats. The key result is that the oscillation is an intrinsic feature of the system itself, not driven by external factors such as seasonality or behavioural changes. The model shows that non-seasonal oscillations, such as those observed for the omicron COVID variant, need no additional explanation such as the appearance of more infectious variants at regular intervals or coupling to behaviour. We infer that the loss of immunity to the SARS-CoV-2 virus occurs on a timescale of about ten weeks.
title Oscillation in the SIRS model
topic Biological Physics
Populations and Evolution
url https://arxiv.org/abs/2504.00670