Ongoing HIV transmission following a large outbreak among people who inject drugs in Athens, Greece (2014-2020)

ABSTRACT Background and Aims The HIV outbreak among People Who Inject Drugs (PWID) in Athens, Greece in 2011-2013 was the largest recent epidemic in Europe and North America. We aim to assess trends in HIV prevalence, drug use and access to prevention among PWID in Athens, to estimate HIV incidence and identify risk factors and to explore HIV-1 dispersal using molecular methods during 2014-2020. Methods Two community-based HIV/hepatitis C programs on PWID were implemented in 2012-2013 (N=3,320) and 2018-2020 (N=1,635) through consecutive Respondent-Driven Sampling (RDS) rounds. PWID were uniquely identified across rounds/programs. We obtained RDS-weighted HIV prevalence estimates per round for 2018-2020 and compared them to 2012-2013. We assessed changes in HIV status, behaviours, and access to prevention in PWID participating in both periods. We estimated HIV incidence in a cohort of seronegative PWID as the number of HIV seroconversions/100 persons-years during 2014-2020 and used Cox regression to identify associated risk factors. Molecular sequencing and phylogenetic analysis were performed in HIV seroconverters. Results HIV prevalence per round ranged between 12.0%-16.2% in 2012-2013 and 10.7%-11.3% in 2018-2020 with overlapping 95% Confidence Intervals (95% CI). Among PWID participating in both programs, HIV prevalence[95% CI] increased from 14.2%[11.7%-17.1%] in 2012-2013 to 22.0%[19.0%-25.3%] in 2018-2020 (p<0.001). There was a deterioration of socioeconomic characteristics such as homelessness (from 16.2%[95% CI: 13.5%-19.2%] to 25.6%[22.3%-29.0%]), a shift in cocaine use (16.6%[13.9%-19.6%] vs. 28.1%[24.7%-31.7%], reduced access to free syringes (51.8%[48.0%-55.7%] vs. 44.5%[40.7%-48.3%]) and a decrease in daily injecting (36.2%[32.6%-39.9%] vs. 28.5%[25.2%-32.1%]). HIV incidence (95% CI) in 2014-2020 was 1.94 (1.50-2.52) new cases/100 person-years and younger age, lower educational level, larger injection network and daily injecting were risk factors. Almost 9% of HIV seroconversions occurred within a newly expanding phylogenetic cluster. Conclusions The ongoing HIV transmission among PWID in Athens provides empirical evidence that the current levels of prevention and treatment are inadequate to control the epidemic. Re-evaluation of prevention programs is urgently needed.