Pharyngeal or nasopharyngeal swabs were taken upon admission in accordance with the protocol from the U.S. Centers for Disease Control and Prevention, as recommended by WHO and the average time between obtaining the samples and testing was 8-48 hours. The laboratory of the University Hospital of Alexandroupolis is a reference center for infectious diseases for more than 350.000 residents and one of the most important reference centers in Nothern Greece. Confirmed case was defined by a positive result of a real-time reversetranscriptase-polymerase-chain-reaction (RT-PCR) [30] .