1. Hospital Policlinico Umberto I, 00161 Rome, Italy
2. Department of Public Health and Infectious Diseases, University of Rome Sapienza, 00185 Rome, Italy
3. Intensive Care Unit, Department of General, Specialistic Surgery, University of Rome Sapienza, 00185 Rome, Italy
4. Infectious and Tropical Disease Unit, Department of Medical and Surgical Sciences, ‘Magna Graecia’ University of Catanzaro, 88100 Catanzaro, Italy
5. Unit of Medical Statistics and Molecular Epidemiology, University Campus Bio-Medico of Rome, 00128 Rome, Italy