Chest Radiographic and CT Findings in Novel Swine-Origin Influenza A (H1N1) Virus (S-OIV) Infection

OBJECTIVE. This article reviews the chest radiographic and CT findings in patients with presumed/laboratory-confirmed novel swine-origin influenza A (H1N1) virus (S-OIV) infection. MATERIALS AND METHODS. Of 222 patients with novel S-OIV (H1N1) infection seen from May 2009 to July 2009, 66 patients (30%) who underwent chest radiographs formed the study population. Group 1 patients (n = 14) required ICU admission and advanced mechanical ventilation, and group 2 (n = 52) did not. The initial radiographs were evaluated for the pattern (consolidation, ground-glass, nodules, and reticulation), distribution, and extent of abnormality. Chest CT scans (n = 15) were reviewed for the same findings and for pulmonary embolism (PE) when performed using IV contrast medium. RESULTS. Group 1 patients were predominantly male with a higher mean age (43.5 years versus 22.1 years in group 2; p < 0.001). The initial radiograph was abnormal in 28 of 66 (42%) subjects. The predominant radiographic finding was patchy consolidation (14/28; 50%) most commonly in the lower (20/28; 71%) and central lung zones (20/28; 71%). All group 1 patients had abnormal initial radiographs; extensive disease involving = 3 lung zones was seen in 93% (13/14) versus 9.6% (5/52) in group 2 (p < 0.001). No group 2 patients had > 20% overall lung involvement on initial radiographs compared with 93% of group 1 patients (13/14). PEs were seen on CT in 5/14 (36%) of group 1 patients. CONCLUSION. Chest radiographs are normal in more than half of patients with S-OIV (H1N1) and progress to bilateral extensive air-space disease in severely ill patients, who are at a high risk for PE.