Table 1.
Initial population distribution of the agent-based model (row percentages).
Table 2.
Key parameter values for injection drug-using (IDU) agents
Table 3.
Key parameter values and sources for non-injection drug-using (NIDU) agents.
Table 4.
Key parameter values and sources for agents who do not use drugs (NU).
Table 5.
Relationship between adherence to HAART, the per-partnership annualized probability of HIV transmission between serodiscordant agents, and progression to AIDS.
Figure 1.
Conceptual framework of the HIV transmission agent-based model.
Arrow represents causal effects between two phenomena in the model. For example, NSP use increases an agent’s probability of HIV testing, which is turn can result in both the knowledge of an HIV positive status and initiation of antiretroviral therapy. Green boxes represent agent characteristics that influence individual agent behavior, denoted in blue. Purple boxes represent interventions that influence these behaviors. Red boxes represent model output.
Figure 2.
Risk network structure at model initialization of a representative subsample of 1000 agents, stratified by drug use status (IDUs, NIDUs, and NUs are represented by red, blue, and green nodes, respectively).
Links indicate sexual activity and/or (if a pair of IDU) injecting event(s) between two agents. In the figures shown above, the average node degree is 1.198.
Figure 3.
HIV prevalence among IDU (panel A) and NIDU (panel B) obtained from a Monte Carlo simulation of the agent-based model.
Black lines indicate empirical trajectories [70]. Error bars represent two standard deviations of the bootstrap estimates; CVAR data for HIV prevalence among NIDU is not available.
Figure 4.
HIV incidence among IDU obtained from a Monte Carlo simulation of the agent-based model.
Data shown in black represent empirically observed estimates HIV incidence among IDU in New York City [36]. Error bars represent two standard deviations of the bootstrapped estimates.
Figure 5.
HIV prevalence among MSM agents obtained from a Monte Carlo simulation of the agent-based model, stratified by drug user status.
Error bars represent two standard deviations of the bootstrap estimates. Abbreviations: MSM = men who have sex with men; NU = non-drug user; NIDU = non-injection drug user; IDU = injection drug user.