Epidemics in a Synthetic Urban Population with Multiple Levels of Mixing

2026-05-18

AI Summary

This study investigates the transmission dynamics of infectious diseases in urban settings under heterogeneous contact patterns. Leveraging census and survey data, the authors construct a geolocated, age-structured synthetic population network that differentiates household, frequent non-household, and sporadic contacts. Incorporating a multi-layered mixing contact structure and a geographically weighted distance-decay assumption, they conduct large-scale agent-based simulations to model epidemic spread in a representative medium-sized Italian city. The findings reveal that age structure substantially accelerates and amplifies outbreak scale, whereas the distance-decay effect exerts only a marginal influence. Notably, the study uncovers a bimodal spatial diffusion pattern within the city, characterized by alternating high- and low-density transmission zones, offering a theoretical foundation for spatially targeted and refined epidemic interventions.

Abstract

Network--based epidemic models that account for heterogeneous contact patterns are extensively used to predict and control the diffusion of infectious diseases. We use census and survey data to reconstruct a geo--referenced and age--stratified synthetic urban population connected by stable social relations. We consider two kinds of interactions, distinguishing daily (household) contacts from other frequent contacts. Moreover, we allow any couple of individuals to have rare fortuitous interactions. We simulate the epidemic diffusion on a synthetic urban network for a typical medium-size Italian city and characterize the outbreak speed, pervasiveness, and predictability in terms of the socio--demographic and geographic features of the host population. Introducing age--structured contact patterns results in faster and more pervasive outbreaks, while assuming that the interaction frequency decays with distance has only negligible effects. Preliminary evidence shows the existence of patterns of hierarchical spatial diffusion in urban areas, with two regimes for epidemic spread in low- and high-density regions.

Problem

• epidemic diffusion
• synthetic population
• contact patterns
• urban network
• spatial transmission

Innovation

• synthetic population
• age-structured contacts
• multi-level mixing
• spatial epidemic diffusion
• urban transmission dynamics