Acute Bronchitis

Overview – Acute Bronchitis

Acute bronchitis is a common lower respiratory tract infection characterized by transient inflammation of the tracheobronchial tree, often following an upper respiratory tract infection. It is typically viral in origin, although bacterial cases do occur. This condition is particularly important to differentiate from pneumonia and other chronic respiratory conditions, given its self-limiting nature and largely supportive management.

Definition

Acute bronchitis is defined as a temporary inflammation of the trachea and bronchi, leading to bronchial oedema and mucus production, usually in the setting of an infection.

Aetiology

Viral Causes (≈80%)

• Rhinovirus
• Coronavirus
• Adenovirus
• Influenza virus
• Parainfluenza virus
• Respiratory Syncytial Virus (RSV)

Bacterial Causes (≈20%)

• Streptococcus pneumoniae (less common)

Pathogenesis

Viral or bacterial infection triggers inflammation of the bronchial epithelium:

• → Bronchial oedema and mucus hypersecretion
• → Airway obstruction
• → Persistent cough and wheeze

Clinical Features

• Recent upper respiratory tract infection (URTI)
• Productive cough (often worse at night)
• Wheezing or chest tightness
• Mild fever (typically not high-grade)
• Normal auscultation in most cases
• Red flags suggesting pneumonia: crackles, dullness to percussion, or focal chest signs

Investigations

• Most cases can be diagnosed clinically without the need for imaging or blood tests.
• Chest X-Ray (CXR): Only if symptoms persist >3 weeks, vital signs are abnormal, or there are focal lung findings
• Spirometry with bronchodilator response: To rule out asthma or COPD in persistent or recurrent cases

Differential Diagnosis

• Upper Respiratory Tract Infection (URTI)
• Asthma or COPD exacerbation
• Sinusitis
• Pneumonia
• Bronchiolitis
• Pertussis (Whooping Cough)
• Gastroesophageal reflux
• Chronic heart failure (CHF)
• Lung cancer (if persistent or with red flags)
• Foreign body aspiration
• Cystic fibrosis

Management

Supportive

• Rest
• Adequate hydration (3–4L/day during febrile periods)
• Paracetamol for fever
• Humidified oxygen (if required)

Pharmacological

• Bronchodilators (e.g. Salbutamol) – may improve symptoms, especially in wheezing
• Antibiotics – only indicated if:
  • Elderly or immunocompromised
  • Significant comorbidities
  • Suspicion of secondary bacterial infection (high fever, purulent sputum)
  • Common choices: Doxycycline or Erythromycin

Summary – Acute Bronchitis

Acute bronchitis is a transient inflammation of the tracheobronchial tree, usually viral and self-limiting. Diagnosis is clinical, with investigations reserved for ruling out more serious pathology. Treatment is supportive in most cases, with antibiotics reserved for specific higher-risk populations. For broader context, visit our Respiratory Overview page.