Using HIV and Hepatitis C Molecular Epidemiology to Investigate Assisted Partner Services Recruitment Among People Who Inject Drugs in Kenya.

Sexual and/or injecting partners of people who inject drugs (PWID) may have an elevated risk of HIV infection either from sharing a transmission network or an epidemiological environment. We estimated the degree of similarity between HIV and hepatitis C (HCV) sequences from PWID and their partners to assess whether partner-based recruitment identifies sexual or injecting partners within transmission networks. We used assisted partner services (APS) to recruit sexual and injecting partners of PWID living with HIV in Kenya and evaluated trends in the TN93 distances (an adjusted measure of sequence similarity) of the HIV-1 and HCV sequences from partner pairs. Of 135 unique pairs identified, 2 sexual, 2 injecting, and 3 unique sexual and injecting partner pairs had HIV sequences within a TN93 distance of 0.045, and 4 unique partner pairs had HCV sequences with distances <0.015. Sexual but not injecting partner pairs had HIV sequences with significantly smaller distances than non-partners, on average, but injecting partner pairs did have significantly smaller HCV-4a patristic distances than non-partners. APS recruitment partly reflects the HIV transmission network among sexual, but not injecting, partners of PWID. The relationship between the injecting partner recruitment and molecular networks is stronger for HCV than HIV and may reflect some recent parenteral HCV transmission. Our results show the importance of continued focus on reducing sexual HIV transmission among PWID and on education and services to address HCV transmission through needle- and/or equipment-sharing.