Characteristic CT findings distinguishing 2019 novel coronavirus disease (COVID-19) from influenza pneumonia

Eur Radiol. 2020 Sep;30(9):4910-4917. doi: 10.1007/s00330-020-06880-z. Epub 2020 Apr 22.


Objectives: To investigate the different CT characteristics which may distinguish influenza from 2019 coronavirus disease (COVID-19).

Methods: A total of 13 confirmed patients with COVID-19 were enrolled from January 16, 2020, to February 25, 2020. Furthermore, 92 CT scans of confirmed patients with influenza pneumonia, including 76 with influenza A and 16 with influenza B, scanned between January 1, 2019, to February 25, 2020, were retrospectively reviewed. Pulmonary lesion distributions, number, attenuation, lobe predomination, margin, contour, ground-glass opacity involvement pattern, bronchial wall thickening, air bronchogram, tree-in-bud sign, interlobular septal thickening, intralobular septal thickening, and pleural effusion were evaluated in COVID-19 and influenza pneumonia cohorts.

Results: Peripheral and non-specific distributions in COVID-19 showed a markedly higher frequency compared with the influenza group (p < 0.05). Most lesions in COVID-19 showed balanced lobe localization, while in influenza pneumonia they were predominantly located in the inferior lobe (p < 0.05). COVID-19 presented a clear lesion margin and a shrinking contour compared with influenza pneumonia (p < 0.05). COVID-19 had a patchy or combination of GGO and consolidation opacities, while a cluster-like pattern and bronchial wall thickening were more frequently seen in influenza pneumonia (p < 0.05). The lesion number and attenuation, air bronchogram, tree-in-bud sign, interlobular septal thickening, and intralobular septal thickening were not significantly different between the two groups (all p > 0.05).

Conclusions: Though viral pneumonias generally show similar imaging features, there are some characteristic CT findings which may help differentiating COVID-19 from influenza pneumonia.

Key points: • CT can play an early warning role in the diagnosis of COVID-19 in the case of no epidemic exposure. • CT could be used for the differential diagnosis of influenza and COVID-19 with satisfactory accuracy. • COVID-19 had a patchy or combination of GGO and consolidation opacities with peripheral distribution and balanced lobe predomination.

Keywords: Coronavirus; Influenza; Pneumonia; Tomography, X-ray; Virus.

MeSH terms

  • Adult
  • Aged
  • Betacoronavirus*
  • COVID-19
  • Coronavirus Infections / diagnostic imaging*
  • Diagnosis, Differential
  • Female
  • Humans
  • Influenza, Human / diagnostic imaging*
  • Male
  • Middle Aged
  • Pandemics
  • Pleural Effusion
  • Pneumonia, Viral / diagnostic imaging*
  • Retrospective Studies
  • SARS-CoV-2
  • Tomography, X-Ray Computed
  • Young Adult