Emerging H7N9 influenza A (novel reassortant avian-origin) pneumonia: radiologic findings

To determine the radiologic findings of human infection with a novel reassortant avian-origin influenza A H7N9 virus in March 2013, the first outbreak in humans.

The institutional review board approved this retrospective study. Twelve patients (nine men and three women) with novel avian-origin influenza A H7N9 virus infection were enrolled. All patients underwent chest radiography and thin-section computed tomography (CT). Lesion patterns, distributions, and changes at follow-up CT were investigated. Two chest radiologists reviewed the images and clinical data together and reached decisions concerning findings by consensus.

At presentation, all patients had progressing infection of the lower respiratory tract, with fever, cough, and shortness of breath, which rapidly progressed to acute respiratory distress syndrome. The imaging findings included ground-glass opacities (GGOs) (in 12 of 12 patients), consolidations (in 11 patients), air bronchograms (in 11 patients), interlobular septal thickening (in 11 patients), centrilobular nodules (in seven patients), reticulations (in seven patients), cystic changes (in four patients), bronchial dilatation (in three patients), and subpleural linear opacities (in three patients). The lung lesions involved three or more lobes in all cases and were mostly detected in the right lower lobe (in 11 patients). Follow-up CT in 10 patients showed interval improvement (in three patients) or worsening (in seven patients) of the lesions. Imaging findings closely mirrored the overall clinical severity of the disease.

Rapidly progressive GGOs and consolidations with air bronchograms and interlobular septal thickening, with right lower lobe predominance, are the main imaging findings in H7N9 pneumonia. The severity of these findings is associated with the severity of the clinical presentation.