Diagnosis: Bronchiolitis
The diagnosis is bronchiolitis—a viral lower respiratory tract infection that is the most common cause of wheezing and respiratory distress in infants aged 1 month to 2 years, characterized by acute inflammation of the small airways with rhinitis, tachypnea, wheezing, and increased respiratory effort. 1, 2
Clinical Presentation Confirms Bronchiolitis
The clinical picture you describe is classic for bronchiolitis in this age group:
- Age 5-6 months falls squarely within the typical bronchiolitis range (peak incidence in infants 1-24 months old) 1, 3
- Respiratory distress with wheezing represents the hallmark lower respiratory tract signs of bronchiolitis, caused by airway edema, epithelial cell necrosis, increased mucus production, and bronchospasm 1, 2
- Non-toxic appearance is typical for most cases of bronchiolitis, which are mild to moderate in severity and can be managed with supportive care 4, 3
Why This is Bronchiolitis and Not Other Diagnoses
Bronchiolitis is diagnosed clinically based on history and physical examination alone—no laboratory tests or imaging are needed or recommended. 2, 3 The diagnosis requires:
- Age less than 2 years 2
- Viral upper respiratory prodrome (often rhinitis, nasal congestion) 1, 2
- Lower respiratory signs including tachypnea, wheezing, crackles, and cough 1, 2
- Increased respiratory effort such as nasal flaring, grunting, or intercostal/subcostal retractions 2
This is NOT asthma because asthma in infants requires recurrent episodes of wheezing triggered by various factors (viral URI, activity, weather changes), with symptoms lasting longer than typical viral illness recovery. 5 A single first episode of wheezing with respiratory distress in a 5-6 month old is bronchiolitis until proven otherwise. 1, 3
Viral Etiology
- Respiratory syncytial virus (RSV) causes 90% of bronchiolitis cases, with peak incidence December through March 1, 4
- Other causative viruses include human metapneumovirus, influenza, adenovirus, and parainfluenza 1
- Nearly 90% of children contract RSV in their first 2 years of life, and up to 40% develop lower respiratory tract infection 1, 4
Critical Assessment Points
While the infant is not toxic-appearing, you must assess for risk factors that predict severe disease:
- Age less than 12 weeks (this infant at 5-6 months is past this highest-risk period) 2, 5
- Prematurity 2, 5
- Hemodynamically significant congenital heart disease 2, 5
- Chronic lung disease 2, 5
- Immunodeficiency 2, 5
Count the respiratory rate for a full 60 seconds—tachypnea ≥70 breaths/minute suggests increased risk of severe disease and potential need for hospitalization. 2
Management Approach
Management is entirely supportive—no medications alter the course of bronchiolitis:
- Assess hydration status and ability to feed orally 1
- When respiratory rate exceeds 60-70 breaths/minute, feeding may be compromised and IV fluids may be needed 1
- Gentle nasal suctioning only when visible congestion affects breathing or feeding 4, 5
- Supplemental oxygen only if SpO2 persistently falls below 90% 1
- Do NOT use bronchodilators, corticosteroids, or antibiotics routinely 1, 5, 3
- Do NOT perform chest physiotherapy—it provides no benefit and may cause harm 1, 5
Common Pitfalls to Avoid
- Do not obtain chest radiographs, RSV testing, or laboratory studies routinely—these do not alter management and may lead to inappropriate antibiotic prescribing 2
- Do not prescribe antibiotics unless there is clear evidence of bacterial co-infection (rare) 1, 5
- Do not use over-the-counter cough and cold medications in children under 2 years—they are contraindicated due to lack of efficacy and potential for serious toxicity including death 5
When to Escalate Care
Provide close follow-up and instruct caregivers to return immediately if: