1. D. Paraskevis 1*, S, Paraschiv 2, V. Sypsa 1, G. Nikolopoulos 3, C. Tsiara 3, G. Magiorkinis 4, M. Psichogiou 5, I. Niculescu 2, I. Batan 2, M. Malliori 5, D. Otelea 2, A. Pharris 7, A. Hatzakis 1 1 National Retrovirus Reference Center, Medical School, University of Athens, Athens, Greece, 2 Molecular Diagnostics Laboratory, National Institute for Infectious Diseases, Bucharest, Romania, 3 Hellenic Center for Diseases Control and Prevention, Athens, Greece, 4 Department of Zoology, University of Oxford, UK, 5 Medical School, University of Athens, Athens, Greece, 6 European Centre for Disease Prevention and Control, Stockholm, Sweden *contact: dparask@med.uoa.gr A comparison of HIV-1 molecular epidemiology among IDUs in Athens and Bucharest: The role of molecular surveillance in Public Health (Poster number TUPDB0105)

2. Introduction In Athens Metropolitan area, during the first months of 2011 an unprecedented upward shift in the number of newly HIV-1 diagnosed IDUs was observed Similarly in Romania, the incidence of HIV-1 among IDUs was increased in the recent years We aimed to identify and compare the characteristics (frequency of HIV-1 clades, transmission patterns and dynamics, origin of infection) of both epidemics by means of molecular epidemiology studies Phylodynamic and phylogeographic analyses were performed on 122 and 557 outbreak sequences collected during 2011- 2013 in Romania and Greece. Additionally we included 3,448 sequences as references Analyses were performed using the current state of the art methods (Bayesian, maximum likelihood methods)

3. Major findings Common features Recent HIV-1 outbreaks among IDUs in Romania and Greece are spreading through three (CRF14_BG and two Fs) and four transmission clusters (CRF14_BG, CRF35_AD, A, B), respectively The majority of infections (>90%) occur within the IDU clusters. Common recombinant viruses (CRF14_BG) are circulating in both regions The CRF14_BG cluster in Greece originated from Romania The exponential phase of epidemic growth was estimated around the 8 th of 2009 and 6 th of 2010 for Bucharest and Athens, respectively

4. Phylodynamic analysis of IDU suboutbreaks from Greece and Romania Romania Greece

5. Major findings Differences All HIV-1 infections (subtype F and CRF14_BG) in Romania originated from locally circulating strains The locally circulating strains in Greece (sub-outbreaks A and B) represent < 20% of infections Conclusion Molecular epidemiology was used to determine the features of the recent outbreaks in Greece and Romania. Our study provides an example about the advances of molecular methods for outbreak investigation and thus for Public Health. Especially in Greece design of interventions for the outbreak were based on findings from our molecular epidemiology studies

6. Acknowledgments Implemented under NSRF 2007-2013 and co-funded by European Social Fund and national resources (MIS 365008). Additional support: NGO Praxis, NGO Positive Voice, Hellenic Scientific Society for the study of AIDS and STDs, The authors would like to acknowledge the contribution of the following persons: Aristotle staff: C. Bagos, M. Esmaili, M. Hasan, E. Karamanou, F. Leobilla, C. Mourtezou, E. Sidrou, M. Zigouritsas, M. Dimitropoulou, N. Kaguelari, M. Michail, S. Papadopoulos, A. Vlahos. Athens University Medical School: V. Benetou, A. Gkegka, E. Hatzitheodorou, P. Iliopoulos, M. Katsimicha, G. Kokolesi, V. Milona, H. Papachristou, C. Rocca, M. Souvatzi, S. Tripou, A. Vassilakis, M. Zavitsanou. Organization Against Drugs: K. Gazgalidis. Greek Reitox Focal Point of the European Monitoring Centre for Drugs and Drug Addiction: A. Fotiou. The volunteers of NGO "Positive Voice" and NGO "Praksis“