A 6-month-old infant presents in winter with 3 days of fever, cough, and progressive respiratory distress. Examination shows subcostal retractions, nasal flaring, diffuse wheeze, and prolonged expiration. SpO2 is 90% on room air. Chest X-ray shows hyperinflation. What is the MOST likely causative organism?

• A Streptococcus pneumoniae
• B Respiratory Syncytial Virus (RSV) ✓
• C Haemophilus influenzae
• D Mycoplasma pneumoniae

Explanation

This is acute bronchiolitis, the most common lower respiratory tract infection in infants under 1 year, occurring in seasonal winter epidemics. Respiratory Syncytial Virus (RSV) is responsible for over 70-80% of cases. The hallmark is diffuse airway obstruction at the bronchiolar level causing hyperinflation, wheeze, and prolonged expiration. Treatment is primarily supportive (oxygen, nasogastric feeds if feeding is poor). Palivizumab (anti-RSV monoclonal antibody) is used as prophylaxis in high-risk premature infants.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.