1. 1st Department of Internal Medicine, Laiko General Hospital, Medical School, National and Kapodistrian University of Athens, 11527 Athens, Greece
2. Department of Hygiene, Epidemiology and Medical Statistics, Medical School, National and Kapodistrian University of Athens, 11527 Athens, Greece
3. Department of Internal Medicine and Infectious Diseases, University General Hospital of Patras, Medical School, University of Patras, 26504 Patras, Greece