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A respiratory condition caused by viral infection, most commonly presenting in infants 3-6 months.

  • Usually self-limiting lasting up to 10 days. Infants may worsen typically up until day 4 of illness before improving.
  • View the full SIGN Guideline


Presentation and Diagnosis

  • Diagnosis is clinical based on history and examination
  • Consensus Definition: 'a seasonal viral illness characterised by fever, nasal discharge and dry, wheezy cough. Fine inspiratory crackles and/or high pitched expiratory wheeze are found on examination'.
  • A coryzal phase of 2-3 days usually preceeds symptoms
  • Typical Features
    • Respiratory distress: tachypnoea, recession, nasal flaring, suprasternal recession, head bobbing.
    • Cough
    • Poor feeding
    • Irritability
    • Fever may be present
    • Apnoea (younger babies)
  • High fever or appearing toxic should prompt consideration of other causes and immediate resuscitation as necessary.

Differential Diagnosis


  • Asthma
  • Pneumonia
  • Congenital lung disease
  • Cystic fibrosis
  • Inhaled foreign body


  • Sepsis
  • Congestive cardiac disease
  • Severe metabolic acidosis

Incidence and Aetiology

Typically affect children under 2 years of age. 90% of children requiring hospitalisation are under 12 months.

  • Respiratory Syncytial Virus (RSV) causes 75% of bronchiolitis
  • During 1st year of life:
    • 70% infected with RSV
      • 22% develop symptomatic disease
    • Therefore one third of all infants under 1yr develop bronchiolitis
    • 3% of infants are admitted to hospital with bronchiolitis in their first year
  • 20% continue with a protracted cough and recurrent viral-induced wheeze (50% of hospital admissions)

  • Seasonality: winter period in temperature climate countries.


  • Oxygen saturations: low sats predict more severe illness
  • Chest Radiography
    • Mild disease: no beneficial information
    • Consider where diagnostic uncertainty or atypical disease course
  • Virological Testing (Nasopharyngeal aspirate, NPA)
    • Rapid testing is recommended to allow cohort management, unless adequate isolation facilities available

  • Blood gas: not usually indicated unless severe disease or beginning to tire.
  • Bacteriology: not routinely indicated
  • Haematology / Biochemistry blood tests: not routinely indicated
  • CRP: no good quality evidence. Not routinely tested.

Admission criteria

Admission to hospital is usually to receive supportive care.

  • Oxygen saturations <92% ('Oxygen requirement')
    • <94% requires careful evaluation
  • Inadequate feeding / hydration.
  • Nasal suction

Infants with significant comorbidities (premature, cardiac, respiratory) are at increased risk of more severe bronchiolitis and have higher rates of hospitalisation.

Limiting Transmission + Cohort Care

RSV is highly infectious through respiratory droplets / secretions in the air and on surfaces. Transmission risk should be minimised by cohort care. RSV can survive 6-12 hours on surfaces, but is destroyed by soap or alcohol gel.


  • Feeding and hydration
    • Small frequent feeds
    • Nasogastric feeds: no evidence it is more or less safe than IV hydration. Concerns re. risk of aspiration in severe distress
    • IV fluids
  • Oxygen
    • Sats <92%
    • Severe respiratory distress
    • Cyanosis
  • CPAP / intubation + ventilation
    • Early discussion with PICU: severe respiratory distress or apnoeas.
  • Nasal suction
    • recommended when nasal blockage is causing respiratory distress.
  • Chest physiotherapy
    • Not recommended outside PICU (percussion or vibration physiotherapy).

RSV hyperimmune globulin is not licensed for use in the UK. Three RCTs demonstrated reduced hospitalisation of premature children or those with bronchopulmonary dysplasia or congenital heart disease.

Discharge Criteria

  • Oxygen saturations
    • Minimum 12 hours saturating >94% in air under observation recommended
  • Feeding - need to be maintaining an adequate daily oral intake
    • >75% normal feeding

Prophylaxis - Palivizumab

Palivizumab, a monoclonal antibody to RSV, does not prevent infection, but is intended to reduce the risk of severe illness when infected.

Cost: (Copied from BNFC 2007 for information only): "By intramuscular injection (preferably in anterolateral thigh). Neonate 15 mg/kg once a month during season of RSV risk." 50-mg vial = £360.40.


  • Routine use not recommended (not cost effective).
  • A lead clinician should identify infants <12 months who may benefit
  • Case-by-case consideration:
    • Extreme prematurity
    • Acyanotic congenital heart disease
    • Congenital or acquired severe lung disease
    • Immune deficiency


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