Azithromycin to Prevent Wheezing Following Severe RSV Bronchiolitis-II

Inclusion Criteria: * Age: 1-18 months. * Hospitalization for the first episode of RSV bronchiolitis. * Confirmed RSV infection by positive nasal swab results (PCR assay and/or direct antigen detection). * At least two of the following symptoms/signs of bronchiolitis: respiratory rate greater than 40 breaths/minute; cough; wheezing; audible rales, crackles, and/or rhonchi; paradoxical chest movements (retractions)28. * Duration of respiratory symptoms from onset of symptoms of the current illness to admission is 120 hours (5 days) or less. * Randomization can be performed within 168 hours (7 days) from onset of symptoms. * Willingness to provide informed consent by the child's parent or guardian. Exclusion Criteria: * Prematurity (gestational age \< 36 weeks). * Presence or history of other significant disease (CNS, lung, cardiac, renal, GI, hepatic disease, hematologic, endocrine or immune disease). Children with atopic dermatitis and/or food allergy will not be excluded from the study. * Clinically significant gastroesophageal reflux currently treated with a daily anti-reflux medication (anti- H2 or PPI). * The child has significant developmental delay/failure to thrive, defined as weight \< 3% for age and gender. * History of previous (before the current episode) wheeze or previous (before the current episode) treatment with albuterol. * History of previous treatment with corticosteroid (systemic or inhaled) for respiratory issues. * Treatment (past or present) with mon…