Eur. Phys. J. B 26, 521-529 (2002)
https://doi.org/10.1140/epjb/e20020122

Epidemic outbreaks in complex heterogeneous networks

¹ The Abdus Salam International Centre for Theoretical Physics, PO Box 586, 34100 Trieste, Italy
² Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya Campus Nord, Mòdul B4, 08034 Barcelona, Spain

Corresponding author: ^a romu@complex.upc.es

Received: 20 September 2001
Revised: 4 February 2002
Published online: 15 April 2002

Abstract

We present a detailed analytical and numerical study for the spreading of infections with acquired immunity in complex population networks. We show that the large connectivity fluctuations usually found in these networks strengthen considerably the incidence of epidemic outbreaks. Scale-free networks, which are characterized by diverging connectivity fluctuations in the limit of a very large number of nodes, exhibit the lack of an epidemic threshold and always show a finite fraction of infected individuals. This particular weakness, observed also in models without immunity, defines a new epidemiological framework characterized by a highly heterogeneous response of the system to the introduction of infected individuals with different connectivity. The understanding of epidemics in complex networks might deliver new insights in the spread of information and diseases in biological and technological networks that often appear to be characterized by complex heterogeneous architectures.