Montelukast in Acute RSV Bronchiolitis

Inclusion Criteria: * Age \> 4 weeks \< 2 years * Duration of respiratory symptoms \< 4 days * Signs of bronchiolitis: prodromal rhinorrhea and cough, followed by at least two of the following signs: chest retractions, tachypnea, wheezing, or rales * First episode of wheezing or shortness of breath * Randomization within 12 hours of admission * No need for steroid treatment in the ward * Informed consent Exclusion Criteria: * A history of asthma symptoms or any previous hospital admissions with respiratory tract illnesses and if they had ever been treated with anti-asthma medications (prior to the current illness). * Underlying cardiopulmonary disease such as bronchopulmonary dysplasia, congenital heart disease, immunodeficiency, or cystic fibrosis.