H1N1 virus infection: chest radiographic findings

To show the plain chest film findings in patients with confirmed infection with the new variant of the influenza A (H1N1) virus and to correlate these findings with the clinical history and evolution.

We reviewed the clinical histories and radiological studies in 99 patients infected with the new variant of H1N1 influenza who were admitted in two Hospitals in Cantabria, Spain. Plain chest film findings were classified according to their parenchymal pattern and the distribution of the lesions.

Of the 99 patients evaluated, 28 had changes on the plain chest film acquired at admission. In these 28 patients, the findings were: condensation in 19, condensation and ground-glass opacities in 7, and ground-glass opacities in 2; the distribution of the lesions was diffuse in 17 patients and bilateral in 17, with the lower and middle lobes being the most frequently affected. The lesions progressed in 13 patients, and the 7 patients who required mechanical ventilation had a higher frequency of diffuse lesion distribution and more lung fields affected on the plain chest field acquired at admission. Pathological findings on plain chest films were more common in males, in smokers, and in patients who presented with shortness of breath, pleuritic pain, and diarrhea (P<0.05).

Most patients infected with the new variant of the H1N1 virus had no alterations on the plain chest film acquired on admission; when findings were present, the predominant pattern was diffuse, bilateral condensation mainly involving the bases of the lungs. Pleural effusion and hilar or mediastinal lymph node enlargement were uncommon.