2.1 Patient recruitment
For this study, patients for whom influenza virus nucleic acid testing
was performed in the microbiology labs of five tertiary hospitals in
China (Supplementary Material 1) from January 1st,
2012 – December 31st, 2019 were screened for
eligibility. Those patients with confirmed Flu-p were enrolled in this
study. Patients were excluded if they: (i) were not classified as having
community-onset pneumonia (hospitalized within the last 28 days, with
pneumonia onset ≥ 48 h after admission [10]), as the inclusion of
nosocomial pneumonia cases had the potential to complicate result
interpretations; (ii) were < 18 years old; (iii) were
immunocompromised, given that this had the potential to adversely impact
influenza clinical outcomes [11]; or (ⅳ) had been intubated prior to
admission.
The study design was approved by the Ethics Committee of Beijing
Jishuitan Hospital (No.201911-15). Given the retrospective nature of the
study, the Ethics Committee determined that an informed consent was not
necessary.