BackgroundDuring 2011, a dramatic increase (1600%) of reported HIV-1 infections among injecting drug users (IDUs) was noted in Athens, Greece. We herein assess the potential causal pathways associated with this outbreak.MethodsOur study employed high resolution HIV-1 phylogenetic and phylogeographic analyses. We examined also longitudinal data of ecological variables such as the annual growth of gross domestic product (GDP) of Greece in association with HIV-1 and HCV sentinel prevalence in IDUs, unemployment and homelessness rates and HIV transmission networks in Athens IDUs before and during economic recession (2008–2012).ResultsIDU isolates sampled in 2011 and 2012 suggested transmission networks in 94.6% and 92.7% of the cases in striking contrast with the sporadic networking (5%) during 1998–2009. The geographic origin of most HIV-1 isolates was consistent with the recently documented migratory waves in Greece. The decline in GDP was inversely correlated with annual prevalence rates of HIV and HCV and with unemployment and homelessness rates in IDUs (all p<0.001). The slope of anti-HCV prevalence in the sentinel populations of IDUs and in “new” drug injectors was found 120 and 1.9-fold (p = 0.007, p = 0.08 respectively) higher in 2008–2012 (economic recession) compared with 2002–2006. The median (25th, 75th) size of transmission networks were 34 (12, 58) and 2 (2, 2) (p = 0.057) in 2008–2012 and 1998–2007, respectively. The coverage of harm reduction services was low throughout the study period.ConclusionsScaling-up harm reduction services and addressing social and structural factors related to the current economic crisis should be urgently considered in environments where HIV-1 outbreaks may occur.

A significant increase (more than 10-fold) in the number of newly diagnosed HIV-1 infections among injecting drug users (IDUs) was observed in Greece during the first seven months of 2011. Molecular epidemiology results revealed that a large proportion (96%) of HIV-1 sequences from IDUs sampled in 2011 fall within phylogenetic clusters suggesting high levels of transmission networking. Cases originated from diverse places outside Greece supporting the potential role of immigrant IDUs in the initiation of this outbreak.

Multiple evidence-based interventions delivered through rapid recruitment in a large proportion of the population of PWID are likely to have helped mitigate this HIV outbreak.

Aims To (i) describe an intervention implemented in response to the HIV-1 outbreak among people who inject drugs (PWIDs) in Greece (ARISTOTLE programme), (ii) assess its success in identifying and testing this population and (iii) describe socio-demographic characteristics, risk behaviours and access to treatment/prevention, estimate HIV prevalence and identify risk factors, as assessed at the first participation of PWIDs. Design A ‘seek, test, treat, retain’ intervention employing five rounds of respondent-driven sampling. Setting Athens, Greece (2012–13). Participants A total of 3320 individuals who had injected drugs in the past 12 months. Intervention ARISTOTLE is an intervention that involves reaching out to high-risk, hard-to-reach PWIDs (‘seek’), engaging them in HIV testing and providing information and materials to prevent HIV (‘test’) and initiating and maintaining anti-retroviral and opioid substitution treatment for those testing positive (‘treat’ and ‘retain’). Measurements Blood samples were collected for HIV testing and personal interviews were conducted. Findings ARISTOTLE recruited 3320 PWIDs during the course of 13.5 months. More than half (54%) participated in multiple rounds, resulting in 7113 visits. HIV prevalence was 15.1%. At their first contact with the programme, 12.5% were on opioid substitution treatment programmes and the median number of free syringes they had received in the preceding month was 0. In the multivariable analysis, apart from injection-related variables, homelessness was a risk factor for HIV infection in male PWIDs [odds ratio (OR) yes versus no=1.89, 95% confidence interval (CI)=1.41, 2.52]while, in female PWIDS, the number of sexual partners (OR for >5 versus one partner in the past year=4.12, 95% CI=1.93, 8.77) and history of imprisonment (OR yes versus no=2.76, 95% CI=1.43, 5.31) were associated with HIV. Conclusions In Athens, Greece, the ARISTOTLE intervention for identifying HIV-positive people among people who inject drugs (PWID) facilitated rapid identification of a hidden population experiencing an outbreak and provided HIV testing, counselling and linkage to care. According to ARISTOTLE data, the 2011 HIV outbreak in Athens resulted in 15% HIV infection among PWID. Risk factors for HIV among PWID included homelessness in men and history of imprisonment and number of sexual partners in women.