Scale-free networks and sexually transmitted diseases: a description of observed patterns of sexual contacts in Britain and Zimbabwe.

Background: Sexually transmitted infections spread through a network of contacts created by the formation of sexual partnerships. In physics, networks have been characterized as "scale-free" if they follow a power law with an exponent between 2 and 3.

Objective: The objective of this study was to test statistically whether distributions of numbers of sexual partners reported from different populations are well described by power laws.