Purpose: to identify differences in CT imaging and clinical features between COVID‐19 and
influenza pneumonia in the early stage, and to identify the most valuable features in the differential
diagnosisDesign: diagnostic case‐control study, retrospective multicentre with historic control groupRecruitment: cases: confirmed SARS‐CoV‐2 patients; controls: influenza pneumonia patients (1 January 2015‐30 September 2019 from 2 hospitals)Sample size: n = 121 (cases = 73)Inclusion criteria: patients confirmed with SARS‐CoV‐2; controls: patients who had 9 respiratory pathogen IgM antibody tested from January 2015‐September 2019Exclusion criteria: cases: not specifiedcontrols:parainfluenza
respiratory syncytial virus
adenovirus
Legionella spp
Mycoplasma pneumoniae
Chlamydia pneumoniae
Coxiella burnetii
aspiration pneumonia
radiation pneumonia
pulmonary contusion
pulmonary oedema
neoplasm
No CT date, no clinical date