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. Author manuscript; available in PMC: 2011 Sep 1.
Published in final edited form as: Epidemiology. 2010 Sep;21(5):676–684. doi: 10.1097/EDE.0b013e3181e6639f

FIGURE 1.

FIGURE 1

Compartmental flows. The natural history of HIV infection is modeled with 3 stages—primary (P), asymptomatic (A), and late stages (L) of infection. The susceptible population is represented with S. The vertical arrows represent removal from the sexually active population. The leftmost horizontal arrow represents susceptible men? entering the sexually active population. The other horizontal arrows represent infection and stage progression with the final arrow being death from AIDS. Parameters are defined in Table 1. Probability of infection (in the arrow from S to P) is explained in Methods section.