<prompt> The most common etiological agent for acute bronchiolitis in infancy isInfluenza virusParainfluenza virusRhinovirusRespiratory syncytial virus  <response>: Most cases of bronchiolitis are caused by the respiratory syncytial virus RSV. RSV is a common virus that infects just about every child by the age of 2. Outbreaks of the RSV infection occur every winter. Bronchiolitis can also be caused by other viruses, including those thatcause the flu or the common cold. Bronchiolitis Lower respiratory tract bronchioles Microbiology : Respiratory syncytial virus RSV Rhinovirus. Parainfluenza virus, Human metapneumovirus Influenza virus Clinical Occurs primarily in children s 2-years-old Often preceded by a 1 to 3 day URI prodrome Fever. Cough Respiratory distress tachypnea, retractions, wheezing, crackles Complications Dehydration Apnea premature and 2 months old Aspiration pneumonia, Respiratory failure Management Nonsevere bronchiolitis Anticipatory guidance, nasal suctioning, hydration Severe bronchiolitis Trial of inhaled bronchodilator controversial Heated humidified high-flow nasal cannula Continuous positive airway pressure Endotracheal intubation Reference: GHAI Essential pediatrics, 8th edition 