Background: Despite the effectiveness of “combined prevention,” outbreaks of rapid HIV transmission have recently occurred in Europe and North America. Understanding how/why these outbreaks occurred should contribute to avoiding future outbreaks.
Methods: A research group among persons interested in outbreaks was formed by the EMCDDA to conduct a systematic review/comparison of the outbreaks. Publications and conference presentations on the outbreaks were compiled and a standardized template was constructed for structured comparisons. A mixed quantitative/qualitative synthesis was developed through successive rounds of data analyses and interpretation among members of the group.
Results: Outbreaks occurred among PWID in Athens, Greece; Bucharest, Romania, Dublin, Ireland; Glasgow, Scotland; Luxembourg; and Scott County, Indiana, United States. There was substantial variation in the size of the outbreaks from under 100 (Dublin, Luxembourg) to over 1100 (Athens, Bucharest) new HIV infections. Outbreaks occurred in areas that had not implemented large-scale combined prevention programming (Athens, Indiana) or where funding was interrupted (Bucharest) but also in areas where combined prevention had been implemented but changes in patterns of drug use (increased use of cocaine or novel psychoactive substances (NPS)) may have led to high rates of injection risk behavior (Bucharest, Dublin, Glasgow, Luxembourg). HCV infection increased rapidly and/or was at very high prevalence prior to several outbreaks (Athens, Bucharest, Glasgow, Indiana, Luxembourg). Community economic problems preceded the outbreaks in Athens, Dublin and Indiana and homeless/economically disadvantaged PWID were particularly vulnerable in all outbreaks. Public health responses included introduction (Indiana) or expansion of standard prevention interventions (syringe service programs, medication-assisted treatment and antiretroviral treatment) but coverage of interventions varied. HIV transmission among PWID has continued in all outbreak locations. Despite substantial decreases in some settings (Athens, Indiana, Dublin), the number of reported cases has not yet been reduced to pre-outbreak levels in any sites.
Conclusions: Complacency for HIV prevention is emerging as an important threat to the success of combined HIV prevention for PWID. Successful HIV prevention for PWID needs to be conceptualized as implementing and maintaining high coverage prevention programs and adapting to changes in patterns of drug use. Particular attention should be paid to NPS, communities undergoing economic difficulties, and homeless PWID.