Epidemic Thresholds on Scale-Free Graphs: the Interplay between Exponent and Preferential Choice

Abstract.We study epidemic threshold properties in a scale-free random graph model. We show via a branching process approximation that the divergence of the second moment of the degree distribution equivalent to the absence of an epidemic threshold. We study further the relation between diameter and epidemic threshold. Absence of an epidemic threshold happens precisely when a positive fraction of the nodes form a cluster of bounded diameter.