Modeling the impact of interventions during an outbreak of HIV infection among people who inject drugs in 2012–2013 in Athens, Greece.

Abstract

BackgroundA large HIV outbreak in People Who Inject Drugs (PWID) occurred in Athens, Greece in 2011–2013. In response, opioid substitution treatment (OST) and needle and syringe programs (NSP) were scaled-up and a seek-test-treat program was introduced in mid-2012. We aim to assess the impact of these interventions. MethodsA mathematical model of HIV transmission among PWID was calibrated to data available over time (2009–2013) on HIV prevalence, NSP/antiretroviral treatment (ART) coverage and high-risk injection. A combined interventions scenario, including decrease in high-risk injection through linkage to OST and modification of risk behaviours and access to NSP and ART, was compared to a counterfactual scenario (no improvement at the levels of these interventions), with HIV incidence being the main outcome. ResultsHIV incidence increased from <0.1 new cases/100 person-years (in 2009) to 11.0 new cases/100 person-years (in 2012). Under both models, a subsequent decline was projected following early 2012, with incidence at the end of 2013 in the combined interventions scenario being lower by 77% compared to the counterfactual. The projected reduction in incidence under the intervention scenario was in agreement with empirical data. HIV prevalence would have escalated to 20.4% (95% CrI: 16.9%, 23.6%) in 2013 under the counterfactual scenario (vs. 16.8% (95% CrI: 11.2%, 23.0%) under the combined interventions scenario). In total, 31.4% of HIV cases (392) were averted over 2012–2013. ConclusionThese results underline the importance of high-coverage harm reduction programs and of community-based interventions to rapidly reach PWID most in need.