Initial HRCT findings of novel influenza A (H1N1) infection.

Objectives: The aim of our study was to describe the presentation and illustrate the imaging features of chest high-resolution computed tomography (HRCT) of patients with novel influenza A (H1N1) virus infection.

Methods: Data were collected from 163 hospitalized patients between November 2009 and March 2011, who fulfilled the clinical criteria for H1N1 influenza infection and underwent HRCT examinations within 24 hours of admission.

Results: Abnormal findings were observed in 40.5% of the patients. The patients with positive imaging findings were significantly older than patients with normal HRCT findings (P=0.02). The most common finding was ground-glass opacity (GGO) (n=35). Interlobular septal thickening (n=31) and centrilobular nodules (n=30) were the second most frequent findings. Other common findings were consolidation, reticulation, and linear shadow. The most common imaging finding for lung involvement was GGO with a patchy pattern. Pulmonary involvement of the disease may be extensive and variable, but the total volume of affected lung was mostly <1 lobe.

Conclusion: The baseline HRCT may be valuable and suggestive even for non-severe H1N1 infections. When a severe case or a evolution is suspected, chest CT could be essential both for determining the precise extent of parenchymal damage and for monitoring its evolution.