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Fluctuation effects in metapopulation models: percolation and pandemic threshold
Marc Barthélemy1, Claude Godrèche, Jean-Marc Luck
1Institut de Physique Théorique, CEA Saclay, and URA 2306, CNRS, 91191 Gif-sur-Yvette, France. marc.barthelemy@cea.fr
Abstract:
Metapopulation models provide the theoretical framework for describing disease spread between different populations connected by a network. In particular, these models are at the basis of most simulations of pandemic spread. They are usually studied at the mean-field level by neglecting fluctuations. Here we include fluctuations in the models by adopting fully stochastic descriptions of the corresponding processes. This level of description allows to address analytically, in the SIS and SIR cases, problems such as the existence and the calculation of an effective threshold for the spread of a disease at a global level. We show that the possibility of the spread at the global level is described in terms of (bond) percolation on the network. This mapping enables us to give an estimate (lower bound) for the pandemic threshold in the SIR case for all values of the model parameters and for all possible networks.
Insights
This study introduces stochastic metapopulation models for disease spread, revealing a connection between global pandemic spread and network percolation. This provides a method to estimate pandemic thresholds for various network structures.
Area of Science:
- Epidemiology
- Network Science
- Mathematical Biology
Background:
- Metapopulation models are standard for simulating disease spread across connected populations.
- Current models often neglect crucial fluctuations by using mean-field approximations.
- Understanding pandemic spread requires accounting for stochasticity in disease dynamics.
Purpose of the Study:
- To develop and analyze fully stochastic metapopulation models for disease spread.
- To analytically investigate the existence and calculation of global pandemic thresholds.
- To establish a connection between disease spread and network percolation theory.
Main Methods:
- Development of fully stochastic metapopulation models for Susceptible-Infected-Susceptible (SIS) and Susceptible-Infected-Recovered (SIR) dynamics.
- Analytical treatment of stochastic models to address disease spread thresholds.
- Mapping the global spread of disease to bond percolation processes on networks.
Main Results:
- Stochastic models allow for analytical solutions regarding disease spread thresholds.
- The global spread of disease is shown to be equivalent to bond percolation on the network.
- An estimate (lower bound) for the pandemic threshold in the SIR model is derived for all parameters and network types.
Conclusions:
- Stochastic metapopulation models offer a more accurate framework for pandemic simulations.
- Network percolation provides a powerful tool for understanding and quantifying pandemic thresholds.
- The findings enable better prediction and management of global disease outbreaks.
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