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# Romantic and sexual networks of adolescents

## Problem

Epidemiologically speaking, it is crucial to understand the contact structure through which disease travels. In studies of sexually transmitted diseases (STDs) in particular, the structure of sexual networks is critical for understanding STD diffusion. Generally, the network structures of disease diffusion and infection can be categorized into four types: the core infection model, the inverse core infection model, the bridging model, and the spanning tree model (see below).
Figure 1. The network structure of four models of infection. For Panels A, B, and C, black circles denote actors that are high-activity or high-risk, and white circles indicate low-activity or low-risk actors. Panel D circles represent randomly selected individuals. Lines represent the relationship between two actors. The dotted lines in Panel A and B delineate the “core”.