Snapshot A 9-month old infant presents with a three-day history of a mild respiratory track infection with serous nasal discharge, fever of 38.5 C, and decreased appetite. Physical exam reveals a tachypneic infant with audible wheezing and a respiratory rate of 65. Flaring of the alae nasi, use of accessory muscles, and subcostal and intercostal retractions are noted. Expiratory wheezes are present. Introduction Acute viral infection of the lower respiratory tract (small airways) Caused by RSV (50% of cases) parainfluenza virus type III adenovirus Results in inflammatory obstruction of the smaller airways Epidemiology usually occurs in children less then 2 years of age peak incidence at 6-12 months Risk factors include infancy (< 6 months) males > female premature birth immunodeficiency underlying cardiopulmonary disease (usually congenital) Presentation Symptoms mild rhinorrhea low-grade fever cough respiratory distress dehydration associated with asthma Physical sxam nasal-flaring tachypnea expiratory obstruction hyperresonance to percussion wheezing and crackles on auscultation Evaluation CXR reveals hyperinflation secondary to obstruction lobar infiltrates and/or atelectasis may be appreciated (20-30% of cases) atelectasis Viral culture may be helpful in achieving diagnosis, though rare guides intervention ELISA (i.e. antigen detection) usually via nasopharyngeal secretions highly sensitive and specific for detection of pathogen Differential Neonatal acute respiratory distress syndrome (ARDS) Treatment Medical management outpatient fluids and nebulizers indicated as outpatient treatment for mild cases leads to full recovery within 1 week in most cases hospitalization and supportive care indicated in severe cases including O2 saturation < 92% premature birth (<34 weeks) toxic appearance age < 3 months underlying cardiopulmonary disease poor parental support system treatment includes contact isolation supplemental O2 bronchodilators (albuterol) IV hydration steroids may be helpful ribavirin use is controversial Prognosis, Prevention, and Complications Prognosis early detection and aggressive, supportive intervention are critical for survival Prevention RSV prophylaxis (via injection with poly- or monoclonal antibodies) indicated in at-risk patients Complications if untreated, can progress to fatal respiratory failure