2.2 Detection of SARS-CoV-2 in respiratory samples
The doctors collected the samples by rubbing 2 of the patient’s nostrils and the posterior oropharynx using separate cotton-tipped swabs. After sampling, the swabs were collected into a single virus collection tube which containing virus preservation solution and sent to the laboratory of Qingdao CDC via dedicated channel. Samples were stored at-20°C if not be analyzed immediately. All samples after sampling were transferred to QMCDCP for SARS-CoV-2 detection. Tests were carried out in biosafety level 2 facilities, using a commercial Novel Coronavirus (2019-nCoV) Nucleic Acid Detection Kit (Shanghai BioGerm Medical Techonology Co., LTD) in a total reaction volume of 25μL, targeting SARS-CoV-2 virus frame1ab (ORF). Viral ribonucleic acid (RNA) was extracted from sample material and collected in elution buffer, and then underwent real-time reverse-transcription-polymerase-chain-reaction (RT-PCR) with SARS-CoV-2-specific primers and probes. Detailed laboratory procedures were referenced and described elsewhere (Hu et al., 2020; Hu et al., 2020).