Human infection with a novel avian-origin influenza A (H7N9) virus: serial chest radiographic and CT findings

Rapidly progressive pneumonia infection with H7N9 virus is a novel disease, and limited information is available concerning serial chest radiographic and computed tomography (CT) findings. The aim of this study was to evaluate the changes in serial radiologic findings in patients with H7N9 pneumonia. The two institutional ethics review boards approved this retrospective study. This study included 10 patients with H7N9 pneumonia. All patients underwent chest radiologic examinations at different time points. Serial radiologic images were systematically analyzed. All patients showed abnormal results on initial chest radiography and CT. The initial radiographic abnormalities were unilateral (n = 9) and bilateral (n = 1), including ground-glass opacities (GGOs) (n = 5) and consolidation (n = 5). The initial CT findings consisted of unilateral (n = 6) and bilateral (n = 4), including consolidation (n = 10), GGOs (n = 10), reticular opacities (n = 2), and pleural effusion (n = 3). Follow-up radiologic findings showed rapid development of consolidation or GGOs within two weeks after illness onset. Pneumomediastinum with secondary subcutaneous emphysema and pneumothorax were noted in two patients. Follow-up high resolution computed tomography (HRCT) after two weeks showed slow improvement in both size and opacity of the lesions. On HRCT after discharge, patients had substantial residual lesions such as irregular linear opacities, reticular opacities, parenchymal bands, traction bronchiectasis, and cystic lesions. The most common radiologic findings at presentation are multifocal or diffuse areas of consolidation and GGOs in H7N9 pneumonia. HRCT in sequence can show more changes in rapid progression of disease and a slow decrease of both size and opacity of the lesions plays an important role in the evaluation of H7N9 pneumonia.