Sample collection and laboratory test
Respiratory samples (throat swabs) were collected from the included ARIs patients within 24 h of hospitalization. Professional staff will rotate the nasopharyngeal swab back and forth 2 to 3 times, then quickly remove the swab and put it into the microbial test tube containing sterile normal saline. Those without phlegm will be atomized and attracted, and the specimen will be immediately sent to the laboratory two hours after collection.
RSV, ADV, Flu A and B, and PIV1, 2, and 3 were detected by direct immunofluorescence technique.  The rapid test kit is provided by Shanghai Haide Diagnostic Co., LTD. (lot number: 186325).  The specific detection principle and results were determined as follows: the nasopharyngeal secretions were repeatedly blown with a capillary straw and transferred to a centrifuge tube at the tip base, centrifuged at (400 ~ 600)×g for 5 ~ 10min to remove the supernatant and leave precipitation.  It is used to add 1 drop of corresponding fluorescent antibody to each cell point of the specimen or photo, incubate in a 37.0 ℃ temperature box for 30min, and then add 1 drop of blocking solution after washing with washing liquid, and observe the results under a fluorescence microscope after sealing the piece. The FITC-labeled virus-specific monoclonal antibody binds to the corresponding viral antigen in the cell to form an antigen-antibody complex. Under the fluorescence microscope, the cells show apple green fluorescence and the negative film is stained red by Evans blue. If two green fluorescent cells are found in each field of vision under the microscope at 200 times, it is positive.