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Respiratory Tract Infections — Detailed Overview

Nelson Textbook of Pediatrics, 22nd Edition

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1. Classification

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2. Common Cold (Acute Viral Rhinitis)

Etiology

• Rhinovirus (>100 serotypes) — most common cause at all ages
• Coronavirus, RSV, parainfluenza, adenovirus, influenza, enterovirus

Epidemiology

• Children average 6–8 colds/year; day-care attendance increases frequency
• Peak incidence: fall and winter

Clinical Features

• Nasal congestion, rhinorrhea (initially clear → mucopurulent), sneezing
• Low-grade fever (more common in infants)
• Sore throat, mild cough
• Duration: 7–10 days

Management

• Supportive only: saline nasal drops, adequate hydration, antipyretics (acetaminophen/ibuprofen)
• Antihistamines, decongestants, and cough suppressants are NOT recommended in children <6 years (no proven benefit; risk of adverse effects)
• Antibiotics not indicated unless secondary bacterial infection

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3. Pharyngitis

Etiology

Clinical Features — GAS Pharyngitis

• Sudden-onset sore throat, fever, headache, abdominal pain
• Tonsillopharyngeal erythema and exudate, palatal petechiae, anterior cervical lymphadenopathy
• Absence of cough, rhinorrhea, conjunctivitis (features suggesting viral etiology)

Diagnosis

• Rapid Antigen Detection Test (RADT): sensitivity ~70–90%, specificity >95%
• Throat culture: gold standard (sensitivity ~90–95%)
• Centor/McIsaac score to guide testing

Management

• Penicillin V (oral) × 10 days — drug of choice; prevents acute rheumatic fever
• Amoxicillin × 10 days — preferred in children (palatability)
• Penicillin G benzathine IM — single dose; ensures compliance
• Penicillin allergy: azithromycin or clindamycin

Complications

• Peritonsillar abscess, retropharyngeal abscess
• Acute rheumatic fever, post-streptococcal glomerulonephritis
• Lemierre syndrome (septic thrombophlebitis of internal jugular vein)

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4. Sinusitis

Etiology (Acute Bacterial)

• Streptococcus pneumoniae (~30%)
• Non-typeable Haemophilus influenzae (~20%)
• Moraxella catarrhalis (~20%)

Diagnostic Criteria (Nelson)

1. Persistent symptoms >10 days without improvement, OR
2. Severe symptoms: fever ≥39°C + purulent nasal discharge for ≥3–4 days, OR
3. Worsening course: symptoms worsen after initial improvement ("double sickening")

Management

• First-line: Amoxicillin (standard or high-dose 80–90 mg/kg/day if risk of resistant pneumococcus)
• Amoxicillin-clavulanate: if no improvement after 72 hours, or severe/complicated disease
• Duration: 10–14 days
• Imaging (CT sinus) only for complications (orbital, intracranial)

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5. Otitis Media

Acute Otitis Media (AOM)

1. Moderate-to-severe bulging of tympanic membrane (TM), or new-onset otorrhea not due to otitis externa
2. Mild bulging of TM + recent onset ear pain (<48 hr) + intense erythema
3. TM perforation with purulent discharge

• <6 months: always treat with antibiotics
• 6–24 months: treat with antibiotics (especially bilateral AOM or with otorrhea)
• ≥2 years: observation acceptable for mild unilateral AOM without otorrhea
• First-line: Amoxicillin 80–90 mg/kg/day × 10 days (5–7 days if ≥2 years, mild)
• Failure at 48–72 hrs: Amoxicillin-clavulanate or IM ceftriaxone

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6. Croup (Laryngotracheobronchitis)

Etiology

• Parainfluenza virus type 1 — most common (60–75%)
• Parainfluenza 2 & 3, RSV, influenza A, adenovirus, human metapneumovirus

Epidemiology

• Peak age: 6 months to 3 years
• Peak season: fall; characteristic nighttime worsening

Clinical Features

• Prodrome of 1–3 days of URI symptoms
• Barking ("seal-like") cough, hoarseness, inspiratory stridor
• Symptoms worse at night and with agitation
• Low-grade to moderate fever

Severity Assessment — Westley Croup Score

Radiology

• Neck X-ray (AP): "Steeple sign" (subglottic narrowing) — supportive but not required

Management

• Observe for rebound after epinephrine (effect lasts 2 hrs); keep ≥3–4 hours post-nebulization
• Humidified air/mist therapy — not evidence-based but commonly used

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7. Epiglottitis

Etiology

• Haemophilus influenzae type b (Hib) — dramatic decline after Hib vaccine
• Post-vaccine era: S. pneumoniae, S. pyogenes, S. aureus, non-typeable H. influenzae

Clinical Features — Classic "4 D's"

• Dysphagia, Drooling, Dysphonia (muffled voice), Distress
• High fever (>39°C), toxic appearance, prefers "tripod" or "sniffing" position
• Sudden onset over hours
• No barking cough (distinguishes from croup)

Management

• Do NOT examine oropharynx or attempt venipuncture until airway secured
• Immediate controlled intubation in OR with ENT/anesthesia present
• Antibiotics: ceftriaxone (covers H. influenzae and other organisms)
• Rifampin prophylaxis for household contacts if Hib confirmed

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8. Bronchiolitis

Etiology

• RSV — responsible for ~50–80% of cases
• Human metapneumovirus, parainfluenza, adenovirus, rhinovirus, bocavirus

Epidemiology

• Peak age: <2 years; most severe in infants <6 months
• Seasonal: winter (RSV season)
• Risk factors for severe disease: prematurity (<32 weeks), BPD, CHD, immunodeficiency, age <3 months

Pathophysiology

Clinical Features

• 2–3 days of URI → tachypnea, wheeze, subcostal/intercostal retractions
• Crackles and prolonged expiration
• Apnea (especially in young infants and ex-premature infants)
• SpO₂ <90–92% is an indicator of severity

Diagnosis

• Clinical diagnosis — no routine testing required
• CXR: hyperinflation, peribronchial thickening, patchy atelectasis (not routinely needed)
• RSV antigen testing if result will change management (e.g., cohorting in hospital)

Management (Nelson / AAP Guidelines)

• Supportive care is the cornerstone
• Oxygen: if SpO₂ <90% (some guidelines use <92%)
• Nasal suctioning before feeds
• Hydration: IV or NG feeds if unable to maintain oral intake
• High-flow nasal cannula (HFNC): used in moderate-severe disease to reduce work of breathing

Prevention

• Palivizumab (RSV monoclonal antibody): monthly IM injections during RSV season for high-risk infants (preterm <29 weeks, hemodynamically significant CHD, CLD of prematurity)
• Nirsevimab: newer long-acting monoclonal antibody; single dose; approved for all infants <12 months before/during first RSV season

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9. Community-Acquired Pneumonia (CAP)

Etiology by Age

Clinical Features

Diagnosis

• CXR: cornerstone of diagnosis; PA and lateral views
• CBC, CRP, procalcitonin (PCT): elevated in bacterial pneumonia
• Blood culture (before antibiotics): positive in <10% but important
• Sputum culture: children <8 years cannot produce adequate specimens
• Urine pneumococcal antigen: not reliable in children
• PCR/respiratory multiplex panels: increasingly used

WHO IMCI Severity Classification

Fast Breathing Thresholds (WHO):

• <2 months: ≥60 breaths/min
• 2–12 months: ≥50 breaths/min
• 1–5 years: ≥40 breaths/min

Management

• Presumed viral (age <5 years, mild): supportive care
• Bacterial/atypical suspected (age ≥5 years): amoxicillin OR azithromycin
• School-age with atypical features: azithromycin (covers Mycoplasma)

Complications

• Parapneumonic effusion / Empyema: most common with S. pneumoniae
  • Small: antibiotic therapy alone
  • Moderate/large or infected: chest tube drainage ± fibrinolysis (urokinase/tPA)
  • Non-responding: VATS (video-assisted thoracoscopic surgery)
• Necrotizing pneumonia: tissue necrosis + pneumatocele formation
• Lung abscess: usually anaerobes; prolonged antibiotics ± drainage
• Pneumothorax, respiratory failure

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10. Pertussis (Whooping Cough)

Etiology

• Bordetella pertussis (primary) and B. parapertussis

Clinical Stages

• Infants <6 months: may present with apnea rather than classic whoop
• Lymphocytosis is characteristic

Diagnosis

• Nasopharyngeal PCR — most sensitive and is the gold standard in paroxysmal stage
• Culture: gold standard but slow (Bordet-Gengou or Regan-Lowe media)
• Serology: useful late in disease

Management

• Azithromycin × 5 days (drug of choice in infants >1 month and older children)
• Erythromycin in neonates <1 month (azithromycin associated with infantile hypertrophic pyloric stenosis — use with caution)
• Azithromycin post-exposure prophylaxis for close contacts
• Hospitalization for infants <6 months, apneic episodes, severe illness

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11. Special Considerations

Recurrent RTIs in Children

• Primary immunodeficiency (IgA deficiency, CVID, X-linked agammaglobulinemia)
• Cystic fibrosis
• Ciliary dyskinesia (primary ciliary dyskinesia / Kartagener syndrome)
• Anatomic anomalies (tracheobronchomalacia, vascular ring, H-type TEF)
• Aspiration (GER, swallowing dysfunction)

Prevention Strategies

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Summary Table

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