H1N1 influenza in an Irish population: patterns of chest radiograph abnormality in patients testing positive.

Abstract

The winter of 2010/2011 saw a second peak in the number of H1N1 cases detected in Ireland. The purpose of this study was to investigate the radiological characteristics of patients diagnosed during this period. A retrospective analysis of these cases was performed. Chest radiographs were classified as normal or abnormal. A total of 37 patients were included. Of these, 22 (59%) of chest radiographs were abnormal and 15 (41%) were normal. In the 7 paediatric patients, 4 (57%) had a perihilar distribution of disease, 2 (28%) had peripherally based disease with 1 (14%) having a mixed distribution. A series of radiographs was available for 9 patients, 6 of these showed a radiographic deterioration from the initial study. The majority of chest radiographs of patients with confirmed H1N1 infection will be abnormal. In children, disease is more likely to be perihilar in distribution. Chest radiography is an important initial investigation in patients with H1N1 infection and is useful to track progression of disease in the subset of patients requiring hospitalization for severe disease.