Various computed tomography findings of 2009 H1N1 influenza in 17 patients with relatively mild illness.

PURPOSE: We retrospectively analyzed the computed tomography (CT) findings of H1N1 virus infection in 17 patients with relatively mild illness.

MATERIALS AND METHODS: From September 2009 to January 2010, a total of 17 patients with confirmed H1N1 infection were included in the study (mean age 30.7 years). All patients were managed as outpatients or required short hospitalization without ventilation assistance. The CT scans were assessed for the presence of nodules, ground glass opacity (GGO), consolidation, bronchial wall thickening, reticulation, effusion, and lymph node enlargement. Location and distribution were evaluated.

RESULTS: The most frequent manifestation was a mixture of nodules, consolidation, and GGO (5/17, 29.4%). In one case there was a focal area of bronchiolitis (centrilobular nodules with tree-in-bud appearance), and 10 of 17 cases (58.8%) showed bronchial wall thickening (findings of bronchitis/peribronchitis) and/or other abnormalities. In 16 of the 17 cases (94.1%) there were CT abnormalities with bilateral and random distribution without zonal predominance. Pleural effusions were seen in eight cases (47.1%).

CONCLUSION: In contrast to several reports so far, CT findings of H1N1 virus infection in patients with mild illness are variable, including suggestive findings of inflammation involving large and/or small airways. This study showed various CT findings overlapping with other viral, atypical, or bacterial pneumonia and even cryptogenic organizing pneumonia.