Snapshot A 1-year-old toddler is brought to the emergency room for trouble breathing. His parents report that for the past few days, he has had low-grade fevers, nasal congestion, and a cough. Today, he did not appear to want to eat or drink any water. On physical exam, he is saturating 88% on room air. He has a prolonged expiratory phase and diffuse wheezes bilaterally. He has nasal flaring and intercostal retractions. He is given supplemental oxygen and admitted for further management. Introduction Classification respiratory syncytial virus (RSV) an enveloped, linear, single-stranded, negative-sense RNA virus with a helical capsid a paramyxovirus causes bronchiolitis in infants and atypical pneumonia Epidemiology incidence more common in the winter demographics children < 2 years of age risk factors daycare centers exposure to air pollutants such as cigarette smoke cardiopulmonary disease immunodeficiency premature infants Pathogenesis the virus contains surface protein F (fusion), which induces respiratory epithelial cells to form multinucleated giant cells the virus initially infects the upper respiratory tract and travels to the lower respiratory tract within a few days edema of submucosa causes an obstructive pathology in the lungs, causing wheezing and respiratory distress Prevention palivizumab mechanism monoclonal antibody against F protein indication premature infants babies at risk of severe infection (i.e., immunocompromised status) Prognosis typically self-limited more severe in infants < 6 months of age Presentation Symptoms low-grade fever a high fever may indicate pneumonia congestion cough poor feeding grunting Physical exam tachypnea bilateral wheezing prolonged expiratory phase increased work of breath nasal flaring intercostal retractions focal crackles in patients with pneumonia Imaging Chest radiography indication suspected pneumonia findings diffuse patchy infiltrates Studies Making the diagnosis most cases are clinically diagnosed Differential Asthma distinguishing factors typically recurrent episodes with identifiable triggers history of atopy in the patient or family Foreign body aspiration distinguishing factor unilateral wheezing Treatment Conservative supportive care indication all patients modalities hydration supplemental oxygen superficial nasal suctioning Complications Hypoxemic respiratory failure treatments oxygen mechanical ventilation