After 5 April, the third period, we developed a screening protocol for patients who were asymptomatic for SARS-CoV-2 infections, described in Fig. 1, in patients who were to undergo surgery. We established several measures before and during admission as well as after the surgical procedure [7, 8]. Before admission, we questioned each patient by telephone to detect those with COVID-19 symptoms. We also requested information about their exposure and confinement status. We recommended that patients record their temperature twice a day, comply with confinement, avoid exposure to family members and go to the hospital the day of the operation with mask and gloves. In the 48 h prior to the surgical procedure, patients went to the hospital for a nasopharyngeal polymerase chain reaction (PCR) test [9] and chest computed tomography (CT).