A Cost–Benefit Approach
Chapter 20: Sex and HIV III: The Role of Networks
We have seen that greater concurrency is one reason why HIV prevalence can vary among countries and among groups. Concurrency is an important component in a network analysis of the spread of HIV. Here we outline other key features of a network analysis that we will use to give a fuller explanation of why it is that African Americans have higher rates of HIV than whites (and Hispanics). We shall see that patterns of population exposure, and not simply individual-level behavior, can determine the spread of HIV. KEY CONCEPTS OF NETWORK ANALYSIS The University of California San Francisco (2003) have produced a publication (prepared by Dan Wohlfeiler and John Potterat) detailing how sexual networks and partner selection can help to explain why African Americans have higher HIV prevalence rates than other races in the United States. We can explain the central ideas by referring to Figures 20.1 and 20.2 based on their work. The network in Figure 20.1 consists of eight individuals (circles), basically in two groups of four. Six of the individuals have two sex partners. Two persons (individuals 4 and 5) have three partners and they are called “core” members. These two core members are also the “bridge” linking the two sets of four. Consider individual 1 to be the index person who has HIV. In just two steps, individual 1 working through individuals 2 and 3 can cause half of the network to be infected. An effective prevention program targeted at the bridge between individuals 4 and...
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