Acute bronchitis is a self-limiting inflammation of the bronchial mucosa, usually following an upper respiratory tract infection (URI). It is most commonly caused by viral pathogens and typically lasts less than three weeks.
Etiology (Causes)
Most cases are viral in origin:
Common Viral Causes:
- Rhinovirus
- Parainfluenza virus
- Influenza A and B
- Respiratory Syncytial Virus (RSV)
- Coronavirus
- Human Metapneumovirus
Less Common (Atypical or Bacterial) Causes:
- Mycoplasma pneumoniae
- Bordetella pertussis
- Chlamydia pneumoniae
Note: A specific pathogen is rarely isolated, and antibiotic therapy is usually not required in otherwise healthy individuals.
Risk Factors
- Smoking
- Chronic Obstructive Pulmonary Disease (COPD)
- Asthma
- Cystic fibrosis
- Bronchiectasis
- Elderly or immunocompromised patients
Pathophysiology
- Infection leads to inflammation and edema of the bronchial epithelium.
- Mucociliary clearance is impaired, and excess mucus production follows.
- The hallmark symptom is persistent cough due to airway irritation.
- In rare cases, infection can progress to bronchiolitis or bronchopneumonia.
Clinical Manifestations
Symptoms
- Persistent cough (initially dry, later productive)
- Sputum: May be clear, purulent, or blood-streaked
- Mild dyspnea
- Chest tightness or pain with breathing
- Low-grade fever
- Fatigue
🔺 High fever or systemic symptoms may suggest pneumonia or influenza.
Physical Exam Findings
- Often normal
- May reveal rhonchi or wheezing
- No signs of consolidation (differentiates it from pneumonia)
Diagnosis
Clinical Diagnosis:
- Based on history and physical examination
- Typical duration: <3 weeks
- Cough >5 days is characteristic
When to Consider Further Testing:
- Chest X-ray: Only if pneumonia is suspected (e.g., abnormal vital signs, hypoxia, rales, consolidation)
- Pertussis testing (nasopharyngeal PCR or culture): If cough >2 weeks with paroxysms or whooping
- Rule out: asthma, postnasal drip, or GERD if chronic cough
Management
Supportive Treatment (Mainstay)
- Rest and hydration
- Analgesics/antipyretics: Acetaminophen or ibuprofen
- Antitussives: Only if cough disturbs sleep (e.g., dextromethorphan, codeine)
Bronchodilators (only if wheezing present):
- Inhaled β2-agonists (e.g., albuterol)
- Inhaled anticholinergics (e.g., ipratropium)
Inhaled corticosteroids:
- Consider if cough persists beyond 2 weeks due to airway hyperreactivity
Antibiotics: Use is Generally Discouraged
Indications for Antibiotics:
- Suspected Pertussis
- COPD exacerbation with at least 2 of the following:
- Increased dyspnea
- Increased cough frequency
- Increased sputum purulence
Recommended Antibiotics (if indicated):
| Drug | Dosage | Duration |
|---|---|---|
| Amoxicillin | 500 mg PO TID | 7 days |
| Doxycycline | 100 mg PO BID | 7 days |
| Azithromycin | 500 mg PO daily | 4 days |
| TMP-SMX (Co-trimoxazole) | 160/800 mg PO BID | 7 days |
🧠Empiric antibiotics have no benefit in most viral acute bronchitis cases and contribute to antimicrobial resistance.
Prognosis
- Symptoms resolve within 10–14 days in most patients.
- Cough may persist for up to 3 weeks due to bronchial hyperresponsiveness.
- Chronic or recurrent cases should be evaluated for underlying lung disease or alternative diagnoses.
Patient Education
- Avoid tobacco smoke and irritants
- Encourage hand hygiene to prevent viral transmission
- Reassure about the benign nature of the condition
- Emphasize the limited role of antibiotics
Key Pearls
- Acute bronchitis is a clinical diagnosis.
- Cough lasting >5 days is often the only symptom.
- Antibiotics are not indicated unless pertussis or COPD exacerbation is suspected.
- Chest X-ray is only warranted if pneumonia is a concern.
- Persistent cough >2–3 weeks → evaluate for asthma, GERD, or postnasal drip.
