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Source: Blackford MG, Glover ML, Reed MD. Lower Respiratory Tract Infections. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th edition. Accessed July 12, 2012.

  • Acute viral infection of lower respiratory tract of infants that affects ~50% of children during first year of life and 100% by 3 years.

  • Most common cause: respiratory syncytial virus (RSV)
  • Other: parainfluenza viruses
  • Bacteria are secondary pathogens in minority of cases.

  • Viral or bacterial invasion of lung parenchyma

  • Occurrence peaks during winter months and persists through early spring.
  • Major reason for hospital admission during first year of life.
  • More common in males than females.

  • RSV prophylaxis in infants with underlying pulmonary or cardiovascular disease
  • Monthly administration during RSV season
    • RSV immune globulin
    • Palivizumab

  • Age <1 year
  • Male gender

  • Prodrome suggesting an upper respiratory tract infection, usually lasting 2–8 days, precedes onset of clinical symptoms.

Signs and Symptoms

  • Prodrome with irritability, restlessness, and mild fever
  • Cough
  • Coryza
  • Vomiting
  • Diarrhea
  • Noisy breathing
  • Increase in respiratory rate
  • Labored breathing with retractions of chest wall, nasal flaring, and grunting
  • Dehydration

Means of Confirmation and Diagnosis

  • History and physical exam
    • Tachycardia and increased respiratory rate
    • Wheezing and inspiratory rales
    • Mild conjunctivitis in one-third of patients
    • Otitis media in 5–10% of patients

Laboratory Tests

  • Complete blood count (CBC): White blood cell (WBC) count normal or slightly elevated.
  • Arterial blood gases
    • Hypoxemia
    • Culture of respiratory secretions: Establishes presumptive diagnosis of infectious bronchiolitis.


  • Chest radiograph to distinguish between illnesses characterized by wheezing

Differential Diagnosis

  • Resolution of signs and symptoms

  • Self-limiting illness usually requiring no therapy unless infant hypoxic or dehydrated.

  • Otherwise healthy infants:
    • Antipyretics
    • Fluids
  • Severe cases:
    • Oxygen therapy
    • IV fluids

  • Antibiotics not routinely administered, but may be used until culture results available.
  • Ribavirin if caused by RSV in patients with underlying pulmonary or cardiac disease, or with severe acute infection

  • Infants with underlying pulmonary or cardiovascular disease
    • RSV prophylaxis
      • Monthly administration during RSV season
        • RSV immune globulin
        • Palivizumab

  • Assess for resolution of symptoms.

  • Self-limited disease in otherwise healthy infant
  • Hospitalization may be necessary if child has underlying cardiac or pulmonary disease.

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