Which of the following is the most frequent agent causing acute bronchiolitis?

الشرح

Core Concept: Acute bronchiolitis is an inflammatory condition of the small airways (bronchioles) primarily affecting infants and young children. It is almost always caused by a viral infection, with Respiratory Syncytial Virus (RSV) being overwhelmingly the most common pathogen.

Clinical Presentation:

• Classic symptoms: Rhinorrhea and mild cough (prodrome) progressing to tachypnea, wheezing, hyperinflation, and increased work of breathing (retractions, nasal flaring). Poor feeding and irritability are common.
• Complications: Apnea (especially in infants < 2 months or premature), respiratory failure, dehydration, and secondary bacterial pneumonia.

Diagnosis:

• First-line diagnostic plan/tool: Clinical diagnosis based on history and physical exam findings in a child under 2 years of age.
• Most accurate (gold standard) diagnostic test: Clinical evaluation. Viral testing (e.g., multiplex PCR or rapid antigen testing of nasopharyngeal aspirates) can identify RSV but is usually reserved for cohorting purposes in the hospital or specific clinical scenarios.

Management:

• Acute management: Hydration and respiratory support (oxygen therapy if hypoxic). Routine use of albuterol, epinephrine, corticosteroids, or antibiotics is not supported by current guidelines.
• Gold standard long-term/definitive management: Supportive care until the viral illness resolves. High-risk infants (e.g., premature, congenital heart disease) may receive monoclonal antibodies (Palivizumab or Nirsevimab) for prophylaxis during RSV season.