Simplified model schematic.

<p>The simplified schematic shows model compartments for PWID not on OAT. A parallel compartment set exists for PWID on OAT, with flows between the two compartment sets, as well as 13 compartments each for men who have sex with men and low-risk populations, yielding a total of 70 active compartments in the model. Individuals age into the model uninfected at age 18 y (external arrow into compartment X₁) and can exit from any compartment (diagonal arrows) due to maturation out of the modeled population (at age 65 y) or death. Solid compartment borders denote awareness of HIV status. ART, antiretroviral therapy; OAT, opioid agonist therapy; PrEP, pre-exposure prophylaxis; PWID, people who inject drugs; Test & Treat, HIV testing and treatment.