What is the primary age group affected by bronchiolitis?

Bronchiolitis Primarily Affects Children Under 2 Years of Age

Bronchiolitis primarily affects infants and young children between 1 month and 23 months of age, with the highest risk in those less than 12 months old, particularly infants younger than 12 weeks. 1

Age Distribution

• Bronchiolitis is the most common lower respiratory infection in young children and the most common cause of hospitalization in those aged less than 1 year 1
• The American Academy of Pediatrics (AAP) specifically defines the target population for bronchiolitis management as children from 1 month through 23 months of age 1
• Approximately 90% of children are infected with Respiratory Syncytial Virus (RSV), the most common cause of bronchiolitis, within the first 2 years of life 1, 2
• Most hospitalizations for bronchiolitis occur in infants less than 1 year old 1, 3

Age-Related Risk Factors

• Infants younger than 12 weeks are at significantly higher risk for severe disease 4, 1
• The highest hospitalization rates are seen in infants under 3 months of age 3
• More than 50% of bronchiolitis-related deaths occur in patients younger than 3 months 3
• The hospitalization rate for bronchiolitis for children under 1 year of age is approximately 3,838 per 100,000 healthy children 3

Clinical Presentation by Age Group

• In infants 1-12 months:

  • More likely to present with increased work of breathing, including tachypnea, nasal flaring, and intercostal retractions 1
  • Higher risk of apnea, particularly in those younger than 1 month and in premature infants 1
  • More severe disease presentation compared to older children 5

• In children 12-24 months:

  • Typically presents with rhinitis and cough that may progress to wheezing and rales 1
  • Generally better able to compensate for increased respiratory effort than younger infants 1
  • Less severe disease presentation 5

High-Risk Groups Within This Age Range

• Premature infants, especially those born before 32 weeks gestation 1
• Children with hemodynamically significant congenital heart disease 1, 2
• Children with chronic lung disease of prematurity 1, 2
• Children with neuromuscular disease or immunodeficiency 1
• Infants with birth weight under 1500 grams 5
• Non-exclusively breastfed infants 5

Clinical Course

• Bronchiolitis is typically self-limiting, with most children recovering within 2-3 weeks 1
• The mean time to cough resolution is 8-15 days 1
• 90% of children are cough-free by day 21 1
• Children with persistent symptoms beyond 4 weeks may represent a different clinical problem, sometimes termed "post-bronchiolitis syndrome" 1

Important Considerations

• Neonates (under 1 month) with bronchiolitis symptoms require special consideration due to their higher risk of severe disease and apnea 1
• The AAP guidelines specifically exclude children with immunodeficiencies, underlying respiratory illnesses, neuromuscular disease, or hemodynamically significant congenital heart disease from general management recommendations 1
• Children outside the 1-24 month age range may develop bronchiolitis-like illnesses but may have different clinical presentations, management needs, and outcomes 1