Chronic pulmonary complications of early influenza virus infection in children.

In 3 male patients, chronic pulmonary sequelae followed influenza virus infection at 5, 24, and 42 months of age. Varying degrees of interstitial fibrosis, bronchial and bronchiolar erosions and metaplasia, obliterative bronchiolitis, and interstitial chronic inflammatory infiltrates were found on lung biopsy. Influenza A/Hong Kong/68 (H3N2) virus was isolated from the lung tissue of one patient 8 weeks after the onset of illness. This is the longest persistence of infectious virus in lung tissue yet reported. Persistent radiographic abnormalities included peribronchial thickening, interstitial densities, bronchiectasis, obliterative bronchiolitis, and segmental atelectasis. Pulmonary function tests showed an obstructive restrictive pattern, with mild improvement after bronchodilation and with deterioration after exercise. These observations suggest that influenza virus infection may be more serious in infants and young children than has been previously recognized and may contribute to the pathogenesis of unexplained interstitial pneumonitis, pulmonary fibrosis, obliterative bronchiolitis, and bronchiectasis.