Seasonality of long term wheezing following respiratory syncytial virus lower respiratory tract infection.

BACKGROUND It is well known that respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) is associated with subsequent wheezing episodes, but the precise natural course of wheezing following RSV LRTI is not known. This study aimed to determine the continuous development of wheezing following RSV LRTI in children up to the age of 3 years. METHODS A prospective cohort study was performed in 140 hospitalised infants with RSV LRTI. Continuous follow up data were obtained with a unique log in which parents noted daily respiratory symptoms. RESULTS A marked decrease in wheezing was seen during the first year of follow up. The burden of wheezing following RSV LRTI was observed during the winter season. Signs of airflow limitation during RSV LRTI were strongly associated with wheezing during the follow up period. Total and specific serum immunoglobulin E levels, patient eczema, and parental history of atopy were not associated with wheezing. CONCLUSIONS Airway morbidity following RSV LRTI has a seasonal pattern, which suggests that viral upper respiratory tract infections are the predominant trigger for wheezing following RSV LRTI. There is a significant decrease in airway symptoms during the first 12 months after admission to hospital. Simple clinical variables, but not allergic risk factors, can predict the development of wheezing following RSV LRTI.