1. National Retrovirus Reference Center, Department of Hygiene, Epidemiology and Medical Statistics, Medical School, University of Athens, Athens, Greece
2. Hellenic Center for Diseases Control and Prevention, Athens, Greece
3. 4th Department of Internal Medicine, Athens University Medical School, Attikon Hospital, Athens, Greece
4. 3rd Department of Internal Medicine, Hellenic Red Cross Hospital, Athens, Greece
5. 1st Department of Internal Medicine, Athens General Hospital 'G. Gennimatas', Athens, Greece
6. 1st Department of Medicine, Athens University Medical School, Laiko Hospital, Athens, Greece
7. Organization Against Drugs (OKANA), Athens, Greece