Ongoing HIV transmission following a large outbreak among people with long term injecting drug use in Athens, Greece (2014-2020)

Background 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 provide updated estimates of HIV prevalence and incidence. Methods Two community-based HIV/hepatitis C programs on active PWID were implemented in 2012-2013 (ARISTOTLE, N=3,320) and 2018-2020 (ARISTOTLE HCV-HIV, N=1,635) through consecutive respondent-driven sampling recruitment rounds. PWID were uniquely identified across rounds/programs. We evaluated trends in HIV prevalence, socioeconomic characteristics, and injection practices in PWID participating in both periods and estimated HIV incidence in a cohort of seronegative PWID. Molecular sequencing and phylogenetic analysis were performed in HIV seroconverters. Results 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% to 25.6%, p<0.001), a shift in the use of cocaine (from 16.6% to 28.1%, p<0.001), reduced access to free syringes (past 12 months: 51.8% and 45.1%, p=0.005) and to HIV testing (past 12 months: 50.9% and 49.4%). HIV incidence (95% CI) in 2014-2015, 2016-2017 and 2018-February 2020 was 2.10 (1.41-3.14), 2.04 (1.34-3.10) and 1.52 (0.84-2.75) new cases/100 person-years, respectively. Younger age, lower educational level, larger injection network and daily injecting were risk factors for HIV seroconversion. Almost 9% of HIV seroconversions occurred within a newly expanding phylogenetic cluster. Conclusion 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, leading to expansion of the pool of infected PWID and a rise in HIV prevalence. Re-evaluation of prevention and treatment programs is urgently needed.