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. Author manuscript; available in PMC: 2016 Mar 1.
Published in final edited form as: J Acquir Immune Defic Syndr. 2015 Mar 1;68(3):264–273. doi: 10.1097/QAI.0000000000000470

Figure 1. “Risk pocket” approach to HESN-IDU subject recruitment in the city of Philadelphia.

Figure 1

High-risk HIV-1 exposed, sero-negative injection drug users (HESN-IDU) were enrolled from the city of Philadelphia via community-based street outreach in specific neighborhoods previously identified as “risk pockets.” Risk pockets are defined as specific neighborhoods with a high HIV-1 incidence where intra-venous drugs are sold, used, and exchanged for sex. Subjects from known risk pockets were identified as HESN-IDU if they reported a history of greater than 2 years of daily injection and frequent (weekly or greater) needle sharing with partners of unknown HIV status. Low-risk non-sharing IDU (NS-IDU) drug-matched subjects were recruited from local needle exchange centers while no-risk unexposed, non drug-users were recruited from the greater Philadelphia area.