Bronchiolitis

Descriptive text is not available for this image BASICS

DESCRIPTION

  • 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

EPIDEMIOLOGY

Incidence

  • 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 of age months with condition, the hospitalization rate is ~2–3%.

Prevalence

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:

  • 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

  • Handwashing 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)
  • CDC recommends (August 2024) that pregnant women receive RSV vaccine (Pfizer Abrysvo—currently only option) between 32 and 36 weeks gestation (if gestational age corresponds to RSV season—September through January). Current data show significant (67%) reduction in hospitalization risk in infants.

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

COMMONLY ASSOCIATED CONDITIONS

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

There's more to see -- the rest of this topic is available only to subscribers.