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Radiol Med. 2012 Mar;117(2):165-84. doi: 10.1007/s11547-011-0734-1. Epub 2011 Oct 21.

H1N1 pneumonia: our experience in 50 patients with a severe clinical course of novel swine-origin influenza A (H1N1) virus (S-OIV).

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  • 1Department of Diagnostic Radiology, A.O. Monaldi, Via Leonardo Bianchi, 80131, Naples, Italy.



The authors reviewed chest radiographs (CXR) and thin-section computed tomography (CT) findings of pulmonary complications in a selected population of 50 consecutive patients with severe novel swine-origin influenza A (H1N1) virus (S-OIV) pneumonia who were seen at the Subintensive Respiratory Unit (UTSIR) and at the Intensive Care Unit (ICU) at Monaldi Hospital, Naples, Italy.


CXR and CT findings of 50 patients who fulfilled the World Health Organisation (WHO) criteria for S-OIV infection were reviewed by four radiologists. The final study group of 50 patients was divided into two subgroups on the basis of clinical course: group 1 consisted of 42 patients requiring noninvasive mechanical ventilation and admitted to the UTSIR; group 2 consisted of eight patients who required ICU admission and extracorporeal membrane oxygenation or advanced mechanical ventilation from October 2009 to December 2009. All patients underwent CXR and thin-section multidetector CT (MDCT) scan; the initial and follow-up radiographs and CT scans were evaluated for the presentation and follow-up pattern (consolidation, ground-glass opacities, nodules, reticulation), distribution and extent of abnormality.


All patients had radiological signs of pulmonary involvement. Ground-glass opacity and consolidation, which was mainly peripheral, was the most frequent finding. In three patients, we report for the first time in viral pneumonia the reversed halo sign. Lesion extent was related to aggressiveness of the illness. More often, both lungs were involved (82%). Thoracic comorbidity was present in 18% of patients; 22% of patients was obese, and in this group, the clinical course was more aggressive than in the others with the same lesion extent at imaging. Furthermore, superinfection led to worsening of the clinical conditions.


The most common CXR and CT findings in patients with S-OIV infection were unilateral or bilateral ground-glass opacities with or without associated focal or multifocal areas of consolidation. On MDCT, ground-glass opacities and areas of consolidation had a predominant peribronchovascular and subpleural distribution, resembling organising pneumonia; they progressed to bilateral extensive airspace disease in severely ill patients.

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