Endemic infectious states below the epidemic threshold and beyond herd immunity

Abstract The COVID-19 pandemic exhibits intertwined epidemic waves with anomalous fade-outs characterized by persistent low prevalence. These long-living epidemic states complicate epidemic control and challenge current modeling approaches. Here we introduce a modification of the Susceptible-Infecte...

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Main Authors: Javier Aguilar, Beatriz Arregui García, Raúl Toral, Sandro Meloni, José J. Ramasco
Format: Article
Language:English
Published: Nature Portfolio 2023-07-01
Series:Communications Physics
Online Access:https://doi.org/10.1038/s42005-023-01302-0
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author Javier Aguilar
Beatriz Arregui García
Raúl Toral
Sandro Meloni
José J. Ramasco
author_facet Javier Aguilar
Beatriz Arregui García
Raúl Toral
Sandro Meloni
José J. Ramasco
author_sort Javier Aguilar
collection DOAJ
description Abstract The COVID-19 pandemic exhibits intertwined epidemic waves with anomalous fade-outs characterized by persistent low prevalence. These long-living epidemic states complicate epidemic control and challenge current modeling approaches. Here we introduce a modification of the Susceptible-Infected-Recovered model in a meta-population framework where a small inflow of infected individuals accounts for undetected imported cases. Focusing on a regime where this external seeding is so small that cannot be detected from the analysis of epidemic curves, we find that outbreaks of finite duration percolate in time, resulting in overall low but long-living epidemic states. Using a two-state description of the local dynamics, we can extract analytical predictions for the phase space. The comparison with epidemic data demonstrates that our model is able to reproduce some critical signatures observed in COVID-19 spreading in England. Finally, our findings defy our understanding of the concept of epidemic threshold and its relationship with outbreaks survival for disease control.
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spelling doaj.art-fb276430585a4584b8f08a292968121a2023-07-30T11:17:26ZengNature PortfolioCommunications Physics2399-36502023-07-016111110.1038/s42005-023-01302-0Endemic infectious states below the epidemic threshold and beyond herd immunityJavier Aguilar0Beatriz Arregui García1Raúl Toral2Sandro Meloni3José J. Ramasco4Instituto de Física Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), Campus UIBInstituto de Física Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), Campus UIBInstituto de Física Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), Campus UIBInstituto de Física Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), Campus UIBInstituto de Física Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), Campus UIBAbstract The COVID-19 pandemic exhibits intertwined epidemic waves with anomalous fade-outs characterized by persistent low prevalence. These long-living epidemic states complicate epidemic control and challenge current modeling approaches. Here we introduce a modification of the Susceptible-Infected-Recovered model in a meta-population framework where a small inflow of infected individuals accounts for undetected imported cases. Focusing on a regime where this external seeding is so small that cannot be detected from the analysis of epidemic curves, we find that outbreaks of finite duration percolate in time, resulting in overall low but long-living epidemic states. Using a two-state description of the local dynamics, we can extract analytical predictions for the phase space. The comparison with epidemic data demonstrates that our model is able to reproduce some critical signatures observed in COVID-19 spreading in England. Finally, our findings defy our understanding of the concept of epidemic threshold and its relationship with outbreaks survival for disease control.https://doi.org/10.1038/s42005-023-01302-0
spellingShingle Javier Aguilar
Beatriz Arregui García
Raúl Toral
Sandro Meloni
José J. Ramasco
Endemic infectious states below the epidemic threshold and beyond herd immunity
Communications Physics
title Endemic infectious states below the epidemic threshold and beyond herd immunity
title_full Endemic infectious states below the epidemic threshold and beyond herd immunity
title_fullStr Endemic infectious states below the epidemic threshold and beyond herd immunity
title_full_unstemmed Endemic infectious states below the epidemic threshold and beyond herd immunity
title_short Endemic infectious states below the epidemic threshold and beyond herd immunity
title_sort endemic infectious states below the epidemic threshold and beyond herd immunity
url https://doi.org/10.1038/s42005-023-01302-0
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