ABSTRACT: 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.
