All confirmed cases were hospitalised and isolated for treatment. The discharge criteria were: (i) afebrile for at least 3 days, (ii) obvious alleviation of respiratory symptoms, (iii) improvement in radiological abnormalities on chest computed tomography (CT) or X-ray and (iv) two consecutive negative detections of SARS-CoV-2 at least 24 h apart [7]. After discharge, all cases were kept under surveillance and quarantined at home for at least 14 days; all cases had a throat swab test for SARS-CoV-2 every day or every other day at least 5 times. For those with positive virus detection during this period, we extracted and analysed the medical records.