Chest radiography and CT findings in patients with the 2009 pandemic (H1N1) influenza.

PURPOSE: To present chest radiography and thoracic computed tomography (CT) findings for patients with pandemic influenza A (H1N1) from November-December 2009 and to explore any differences compared to previously reported imaging findings.

MATERIALS AND METHODS: Fifty-two hospitalized patients with pandemic influenza (H1N1) were included in the study. All of the patients underwent chest radiography, and 28 patients were also evaluated by thoracic CT. Group 1 comprised 24 (46%) patients with no identified risk factors for H1N1 influenza infection. Group 2 comprised the remaining 28 (54%) patients with identified risk factors. The distribution of lung involvement, consolidation, ground-glass opacity (GGO), lymph nodes, and pleural effusion were evaluated.

RESULTS: Abnormal findings were observed in 85% of the patients. Bilateral lung involvement was present in 80% of the patients. The most common finding was a mixture of GGO and air-space consolidation. Lower zone predominance occurred in 89% of group 1 and 85% of group 2 patients. The involvement was observed most frequently in the peripheral and central perihilar areas of the lung in 80% of the patients. The extent of disease was greater in group 2 patients with the involvement of three or more lung zones in 62% of the patients.

CONCLUSION: The most common imaging finding for lung involvement was a mixture of air-space consolidation and GGO with a patchy pattern and lower/middle zone predominance. Pulmonary involvement of the disease was more extensive than that described in previous reports.