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).