Seasonal synchronization and unpredictability in epidemic models with waning immunity and healthcare thresholds

Abstract This paper explores a model integrating healthcare capacity thresholds and seasonal effects to investigate the synchronization of epidemic cycles with seasonal transmission rates, using parameters reflective of the COVID-19 pandemic. Through bifurcation analysis in the epi-seasonal domain,...

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Main Authors: Veronika Eclerová, Deeptajyoti Sen, Lenka Přibylová
Format: Article
Language:English
Published: Nature Portfolio 2025-05-01
Series:Scientific Reports
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Online Access:https://doi.org/10.1038/s41598-025-01467-4
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author Veronika Eclerová
Deeptajyoti Sen
Lenka Přibylová
author_facet Veronika Eclerová
Deeptajyoti Sen
Lenka Přibylová
author_sort Veronika Eclerová
collection DOAJ
description Abstract This paper explores a model integrating healthcare capacity thresholds and seasonal effects to investigate the synchronization of epidemic cycles with seasonal transmission rates, using parameters reflective of the COVID-19 pandemic. Through bifurcation analysis in the epi-seasonal domain, we identify regions of significant seasonal synchronization related to transmission rate fluctuations, waning immunity, and healthcare capacity thresholds. The model highlights four sources of unpredictability: chaotic regimes, quasiperiodicity, proximity to SNIC or transcritical bifurcations, and bistability. Our findings reveal that chaotic regimes are more predictable than quasiperiodic regimes in epidemiological terms. Synchronizing outbreaks with seasonal cycles, even in chaotic regimes, predominantly results in significant winter outbreaks. Conversely, quasiperiodicity allows outbreaks to occur at any time of the year. Near eradication unpredictability aligns with historical pertussis data, underscoring the model’s relevance to real-world epidemics and vaccine schedules. Additionally, we identify a bistability region with potential for abrupt shifts in disease prevalence, triggered by superspreading events or migration.
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spelling doaj-art-1a9b404efe924be6bd37804c52f068d82025-08-20T03:10:17ZengNature PortfolioScientific Reports2045-23222025-05-0115112010.1038/s41598-025-01467-4Seasonal synchronization and unpredictability in epidemic models with waning immunity and healthcare thresholdsVeronika Eclerová0Deeptajyoti Sen1Lenka Přibylová2Department of Mathematics and Statistics, Faculty of Science, Masaryk UniversityDepartment of Mathematics and Statistics, Faculty of Science, Masaryk UniversityDepartment of Mathematics and Statistics, Faculty of Science, Masaryk UniversityAbstract This paper explores a model integrating healthcare capacity thresholds and seasonal effects to investigate the synchronization of epidemic cycles with seasonal transmission rates, using parameters reflective of the COVID-19 pandemic. Through bifurcation analysis in the epi-seasonal domain, we identify regions of significant seasonal synchronization related to transmission rate fluctuations, waning immunity, and healthcare capacity thresholds. The model highlights four sources of unpredictability: chaotic regimes, quasiperiodicity, proximity to SNIC or transcritical bifurcations, and bistability. Our findings reveal that chaotic regimes are more predictable than quasiperiodic regimes in epidemiological terms. Synchronizing outbreaks with seasonal cycles, even in chaotic regimes, predominantly results in significant winter outbreaks. Conversely, quasiperiodicity allows outbreaks to occur at any time of the year. Near eradication unpredictability aligns with historical pertussis data, underscoring the model’s relevance to real-world epidemics and vaccine schedules. Additionally, we identify a bistability region with potential for abrupt shifts in disease prevalence, triggered by superspreading events or migration.https://doi.org/10.1038/s41598-025-01467-4SIRS modelSeasonalityBifurcationChaosQuasiperiodicity
spellingShingle Veronika Eclerová
Deeptajyoti Sen
Lenka Přibylová
Seasonal synchronization and unpredictability in epidemic models with waning immunity and healthcare thresholds
Scientific Reports
SIRS model
Seasonality
Bifurcation
Chaos
Quasiperiodicity
title Seasonal synchronization and unpredictability in epidemic models with waning immunity and healthcare thresholds
title_full Seasonal synchronization and unpredictability in epidemic models with waning immunity and healthcare thresholds
title_fullStr Seasonal synchronization and unpredictability in epidemic models with waning immunity and healthcare thresholds
title_full_unstemmed Seasonal synchronization and unpredictability in epidemic models with waning immunity and healthcare thresholds
title_short Seasonal synchronization and unpredictability in epidemic models with waning immunity and healthcare thresholds
title_sort seasonal synchronization and unpredictability in epidemic models with waning immunity and healthcare thresholds
topic SIRS model
Seasonality
Bifurcation
Chaos
Quasiperiodicity
url https://doi.org/10.1038/s41598-025-01467-4
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AT lenkapribylova seasonalsynchronizationandunpredictabilityinepidemicmodelswithwaningimmunityandhealthcarethresholds