Incidence and predisposing factors for severe disease in previously healthy term infants experiencing their first episode of bronchiolitis

Aim: To determine the incidence and predisposing factors for severe bronchiolitis in previously healthy term infants < 12 months of age experiencing their first episode of bronchiolitis. Methods: Epidemiological, clinical and virological data were prospectively collected. Severity was assessed by the need for ventilatory support. Results: Of the 310 infants enrolled, 16 (5.1%) presented with severe bronchiolitis requiring ventilatory support (11 since admission). Compared with infants with less severe bronchiolitis, infants with severe disease presented with lower birth weight, gestational age, postnatal weight and postnatal age, and were more likely to be born by cesarian section. C-reactive protein positive results (> 0.8 mg/dL) and pulmonary consolidation on chest X-ray were more common among infants with severe disease. Severity was independently associated with younger age on admission < 30 days, respiratory syncytial virus (RSV) infection and lymphocyte counts < 3200/mu L. No significant differences were found between epidemiologic variables. Conclusions: Severe bronchiolitis is uncommon in previously healthy term infants < 12 months of age and when present develops soon after disease onset. Severity is predicted by young age and RSV carriage, whereas epidemiologic variables seem less likely to intervene.