Functional laws of large numbers (FLLNs) describe the mean-field trajectory of epidemics on networks, but say nothing about the fluctuations around it. These fluctuations are governed by moments of the degree distribution not relevant at the level of the mean. A rigorous functional central limit theorem (FCLT) exists for the susceptible--infected ($SI$) process on configuration-model graphs, but no analogue exists for $SIS$, where recovery reintroduces vertices into the susceptible pool with partially known neighborhoods, breaking the clean neighborhood distribution the $SI$ derivation relies on. We develop a tractable variance approximation for Markovian $SIS$ on configuration-model graphs, combining Gleeson's approximate master equation (AME) framework with a van Kampen system-size expansion in the spirit of the $SI$ FCLT. We derive a closed drift and diffusion matrix for a reduced susceptible/$SI$-edge/$SS$-edge count vector and obtain the time-dependent covariance via the associated Langevin/Lyapunov equation. Validation against Gillespie simulation across Poisson, regular, and power-law networks shows close agreement, with deviations near the epidemic threshold and in strongly heterogeneous networks.
Extreme epidemic risk is controlled by the right tail of the outbreak-size distribution, but this distribution is generally unknown for non-Markovian spreading on networks. Here we determine this distribution by mapping non-Markovian SIR dynamics to an effective Markovian description. We show that arbitrary infection and recovery time statistics can be incorporated through a single edge transmissibility, yielding an effective Markovian process that reproduces the full outbreak-size statistics. For weakly heterogeneous networks, the reduction yields a universal well-mixed semiclassical theory governed by the bond-percolation reproductive number. Outbreak statistics across diverse waiting-time distributions and topologies collapse onto one predictive curve. For highly heterogeneous and empirical networks, the corresponding effective Markovian dynamics on the network captures the complete distribution. Our results provide a direct route from measured waiting-time distributions to quantitative predictions of network-level extreme-outbreak risk.
We consider a model for the spread of an infection within an interacting particle system on $\mathbb{Z}^d$, generalizing a framework introduced by Kesten and Sidoravicius to a zero-range process in equilibrium with density $\rho>0$. In our model, at any time, individuals are either healthy or infected. The infection spreads instantaneously whenever infected and healthy particles occupy the same site, while infected particles heal independently at rate $\delta>0$. We investigate the extinction-survival phase diagram of this process starting from a configuration where only the particles at the origin are infected. For every fixed positive healing rate, we prove that the infection becomes extinct almost surely if the density $\rho$ is sufficiently small and survives with positive probability if $\rho$ is sufficiently large, establishing the existence of a non-trivial critical density. At sufficiently high densities, survival occurs even under instantaneous healing. We also show that, for every positive density, the infection survives when the healing rate is sufficiently small.
Rangel Baldasso, Marcelo R. Hil'ario, Ian Ornelas· 0 citations
The analysis of random walks on networks often relies on global quantities that average over nodes, thereby masking local differences in diffusion speed. This study introduces a vertex-level quantity Hi, defined as the finite-window fitted scaling exponent of the mean squared resistance distance ⟨Ωi2(t)⟩∼Cit2Hi from a given node i. We found nodes with Hi values below 0.5 (echo effect) and above 0.5 (catapult effect). The exponent is computed exactly via matrix powers of the transition matrix. We systematically evaluate Hi on several synthetic network families, generalized Sierpiński graphs, Newman-Watts small-world networks, and a custom grid-path-complete graph, and on two real-world networks (international E-road network and western U.S. power grid). We found nodes with Hi values less than 0.5 (subdiffusive regime) and greater than 0.5 (apparent superdiffusion) in both model networks and real-world networks. Analysis of model networks shows that when a node has an echo effect, its Hi value is less than 0.5, whereas when it has a catapult effect, its Hi value is greater than 0.5. In the two real networks, most nodes are in the subdiffusive regime and the overall heterogeneity of the local diffusion exponents is low, as indicated by Rényi indices of 0.0835 (E-road network) and 0.0555 (power grid). Comparisons with classical centrality measures indicate that Hi provides information not captured by those measures. The local diffusion exponent offers a vertex-level, dynamics-based tool for identifying structural bottlenecks and node roles, complementing global network characterizations.
This paper provides the rigorous mathematical foundations and algorithmic details underlying the CPMC framework, and details a dynamic programming scheme to exactly implement complex boundary conditions - including patient-zero and macroscopic outbreak-size constraints - enabling the rejection-free generation of valid trajectories.
Thomas Barthel, Jiazheng Sun, Jhao-Hong Peng· 1 citation
In this paper, we propose and analyze a diffusion time-changed susceptible-infected-susceptible (SIS) epidemic model driven by time-changed Brownian motion. We prove that the proposed model admits a unique global positive solution for any initial value in $(0,N)$. The extinction and persistence of the disease are then investigated. To approximate the diffusion time-changed SIS model, we construct a positivity-preserving logarithmic Euler-Maruyama (LEM) method. Assuming that the time-changed is given by the inverse of a standard $\alpha$-stable subordinator with $\alpha\in(0,1)$, we prove that the numerical solution converges strongly to the exact solution with order $\alpha$. Finally, numerical experiments are provided to confirm the predicted convergence rates and illustrate the positivity-preserving property of the proposed method.
In this paper we develop a probabilistic framework for quantifying the economic impact of epidemics under prevalence-based control policies. The epidemic dynamics are described by a novel continuous-time Markovian SIR model in which the infection rates and the cost structure switch when the number of infectious cases crosses a critical threshold. On top of the stochastic dynamics, we consider a state-dependent cost framework that distinguishes (i) time-in-state sojourn costs, (ii) per-infection costs and (iii) activation/deactivation expenses associated with implementing and lifting control measures. Within this setting, we define the total epidemic cost and the cost of a tagged infectious individual as random variables and derive recursive expressions for their Laplace–Stieltjes transforms (LSTs) and moments. Using matrix differential calculus and Kronecker products, we further obtain recursive formulas for the sensitivities and elasticities of the most representative moments, with respect to the main cost parameters. Numerical experiments illustrate how different cost components drive the mean and standard deviation of total and individual costs across a range of thresholds and epidemic scenarios. The proposed methodology thus combines stochastic epidemic modeling and perturbation analysis to provide distribution-aware, parameter-sensitive assessments of epidemic costs, with direct relevance for statistical evaluation and operations research methods in policy design.
Vasileios E. Papageorgiou, A. Economou· Methodology and Computing in...· 0 citations
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