Interplay between intra-urban population density and mobility in determining the spread of epidemics

TL;DR

This study uncovers how urban population density and human mobility patterns influence epidemic spread, revealing that targeted mobility restrictions in high-density centers can effectively mitigate outbreaks.

Contribution

It introduces a formal framework linking urban density, mobility flows, and epidemic vulnerability, and proposes targeted mitigation strategies based on these insights.

Findings

Mobility between high-density centers increases epidemic risk.

Heterogeneity in COVID-19 spread across US cities explained by mobility patterns.

Asymmetric mobility restrictions can effectively reduce epidemic spread.

Abstract

In this work, we address the connection between population density centers in urban areas, and the nature of human flows between such centers, in shaping the vulnerability to the onset of contagious diseases. A study of 163 cities, chosen from four different continents reveals a universal trend, whereby the risk induced by human mobility increases in those cities where mobility flows are predominantly between high population density centers. We apply our formalism to the spread of SARS-COV-2 in the United States, providing a plausible explanation for the observed heterogeneity in the spreading process across cities. Armed with this insight, we propose realistic mitigation strategies (less severe than lockdowns), based on modifying the mobility in cities. Our results suggest that an optimal control strategy involves an asymmetric policy that restricts flows entering the most vulnerable areas but allowing residents to continue their usual mobility patterns.