• Inflammation and obstruction of small airways and reactive airways generally affecting infants and young children; manifests as an upper respiratory infection (URI) prodrome followed by increased respiratory effort, crackles, and wheezing
  • Usual course: insidious, acute, progressive with a variable duration; some experience persistent symptoms (primarily cough) for 14 to 21 days.
  • Leading cause of hospitalizations in infants and children in most Western countries; it is the most common cause of lower respiratory tract infections (LRTI) in children <24 months of age.
  • Predominant age: newborn to 2 years (peak age <6 months); neonates are not protected despite transfer of maternal antibody.
  • Predominant sex: male > female



  • Accounts for ~$1.7 billion in health care costs in the United States; incidence is estimated at 3.2/1,000. Almost 100% of children experience RSV infection by two seasons.
  • Usually seasonal (October to May in the Northern Hemisphere) and often occurs in epidemics—in subtropical regions; RSV is endemic year-round.
  • Responsible for 18.8% (90,000 annually) of all pediatric hospitalizations (excluding live births) in children aged <2 years
  • Incidence is increasing since 1980 (with concomitant increase in relative rate of hospitalization from 2002 to 2007); of those <12 months of age with condition, the hospitalization rate is ~2–3%.

There is a 21–25% prevalence of bronchiolitis in children <12 months of age, decreasing to 13% from 12 to 24 months of age in the United States.

Etiology and Pathophysiology

RSV accounts for 70–85% of all cases (children <12 months of age), but rhinovirus, parainfluenza virus, metapneumovirus, adenovirus, influenza virus, Mycoplasma pneumoniae, and Chlamydophila pneumoniae have all been implicated (1):

  • Infection results in necrosis and lysis of epithelial cells and subsequent release of inflammatory mediators.
  • Edema and mucus secretion, which combined with accumulating necrotic debris and loss of cilia clearance, result in airflow obstruction.
  • Ventilation/perfusion mismatching, which may result in hypoxia
  • Air trapping is caused by dynamic airways narrowing during expiration, which increases work of breathing.
  • Bronchospasm appears to play little or no role.

Risk Factors

  • Secondhand cigarette smoke
  • Low birth weight, premature birth (especially those infants born <35 weeks’ gestation)
  • Immunodeficiency—both congenital and acquired
  • Formula-fed infants
  • Contact with infected person (primary mode of spread)
  • Children in daycare environment
  • Congenital cardiopulmonary disease
  • Comorbid neurologic disorder
  • <12 weeks of age

General Prevention

  • Hand washing or use of alcohol-based hand rubs (preferred)—this simple exercise has been estimated to have the largest impact on prevention of transmission.
  • Contact isolation of infected babies
  • Persons with colds should keep contact with infants to a minimum.
  • Breastfeeding of infants for at least 6 months has been associated with reduced morbidity of disease.
  • Palivizumab (Synagis), a monoclonal product, administered monthly, October to May, 15 mg/kg IM; used for RSV prevention only in high-risk patients (see American Academy of Pediatrics [AAP] recommendations) (2)

Pediatric Considerations
Prior infection does not seem to confer subsequent immunity.

Commonly Associated Conditions

  • Upper respiratory congestion
  • Conjunctivitis
  • Pharyngitis
  • Otitis media
  • Diarrhea

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