1. Department of Experimental and Clinical Medicine (DMSC), University of Florence Medical School, I‑50139 Florence, Italy
2. Department of Paediatric Radiology, ‘Mitera’ Children's Hospital, 15123 Athens, Greece
3. Paediatric Clinic, Aliveri, 34500 Island of Euboea, Greece
4. COVID-19 Reference Centre, ‘Rafina’ Health Care Centre, 19009 Rafina, Greece
5. Paediatric Intensive Care Unit (PICU), University Hospital of Patras, 26504 Rio, Greece
6. First Department of Paediatrics, University of Athens School of Medicine, 11527 Athens, Greece
7. Laboratory of Clinical Virology, School of Medicine, University of Crete, 71003 Heraklion, Greece