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. Author manuscript; available in PMC: 2017 Mar 1.
Published in final edited form as: Math Biosci. 2016 Jan 14;273:102–113. doi: 10.1016/j.mbs.2016.01.003

Figure 1.

Figure 1

Model schematic. We consider a population of male and female IDUs. At each time step t = 1, 2, … individuals can join or leave the population through initiating or abstaining from injection drug use. Each IDU can be associated with a number of characteristics including gender, age, disease status, disease awareness and treatment status, and drug abuse treatment status. We consider heterosexual and needle-sharing relationships, and one or more diseases (e.g., HIV, HCV) being spread via risky sexual and/or needle-sharing contacts. We distinguish two types of sexual partnerships: regular and casual partnerships. We distinguish two types of needle-sharing relationships: long-term needle-sharing and one-time needle-sharing (not represented in the risk network). We allow relationships to dissolve and form dynamically; thus the disease(s) can spread to any individuals who ever engage in risky behaviors.