Epidemic outbreaks in complex heterogeneous networks

We present a detailed analytical and numerical study for the spreading of\ninfections in complex population networks with acquired immunity. We show that\nthe large connectivity fluctuations usually found in these networks strengthen\nconsiderably the incidence of epidemic outbreaks. Scale-free networks, which\nare characterized by diverging connectivity fluctuations, exhibit the lack of\nan epidemic threshold and always show a finite fraction of infected\nindividuals. This particular weakness, observed also in models without\nimmunity, defines a new epidemiological framework characterized by a highly\nheterogeneous response of the system to the introduction of infected\nindividuals with different connectivity. The understanding of epidemics in\ncomplex networks might deliver new insights in the spread of information and\ndiseases in biological and technological networks that often appear to be\ncharacterized by complex heterogeneous architectures.\n