About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Acute cough (<3 weeks) due to lower respiratory tract inflammation — predominantly viral
- Typically self-limiting within 3 weeks; cough may persist for up to 6 weeks
- NICE NG120: antibiotics are NOT routinely recommended — no significant benefit in uncomplicated acute bronchitis
- Green/purulent sputum does NOT automatically indicate bacterial infection or need for antibiotics
- Red flags suggesting pneumonia: high fever (>38°C), tachycardia, tachypnoea, focal chest signs, SpO2 <94%
Overview
Acute bronchitis is a self-limiting inflammation of the tracheobronchial tree, most commonly caused by viral infection (rhinovirus, influenza, parainfluenza, RSV, adenovirus, coronavirus). It presents with acute cough that may be productive, often following an upper respiratory tract infection. The condition is distinguished from pneumonia by the absence of focal chest signs, significant fever, and systemic illness. It is one of the most common reasons for GP consultation and a major driver of inappropriate antibiotic prescribing.
Epidemiology
Acute bronchitis is extremely common, affecting approximately 5% of adults per year. It peaks in autumn and winter. Most cases are viral. It is a leading cause of inappropriate antibiotic prescribing — NICE estimates that antibiotics provide minimal benefit (reducing cough duration by less than 1 day) while contributing to antimicrobial resistance and side effects.
Clinical Features
Symptoms
Acute cough (may be dry or productive)
Sputum production (may be clear, white, yellow, or green — colour alone does NOT indicate bacterial infection)
Sore throat, rhinorrhoea, malaise (preceding URTI symptoms)
Mild chest discomfort or tightness
Low-grade fever (≤38°C)
High fever >38°C, haemoptysis, significant breathlessness — consider pneumonia
Signs
Chest examination is typically NORMAL or shows scattered wheeze/rhonchi
No focal consolidation on auscultation
Focal crackles, bronchial breathing, dullness to percussion — suggests pneumonia
Tachypnoea >20/min, tachycardia >100, SpO2 <94% — consider pneumonia or alternative diagnosis
Investigations
First-line
Clinical diagnosisNo investigations needed in uncomplicated acute bronchitis in a well patient
Second-line
CRP point-of-care testingIf diagnostic uncertainty: CRP <20 mg/L → antibiotics unlikely to help; CRP 20–100 → consider delayed prescription; CRP >100 → consider antibiotics (likely pneumonia)
Chest X-rayOnly if pneumonia suspected (focal signs, SpO2 <94%, significant systemic illness) or symptoms >3 weeks
1
Self-care and reassurance
- Explain that acute bronchitis is usually viral and self-limiting
- Cough typically resolves within 3 weeks but may persist up to 6 weeks
- Adequate hydration, rest, paracetamol or ibuprofen for symptom relief
- Honey and lemon (adults and children >1 year) may help cough symptoms
2
Antibiotics
- NICE NG120: do NOT routinely offer antibiotics for acute bronchitis
- Consider immediate antibiotics only if: systemically very unwell, pre-existing comorbidity with high risk of complications (e.g. immunosuppression, significant heart/lung/renal/liver disease), or CRP >100
- Consider a delayed (back-up) antibiotic prescription if CRP 20–100 or clinical uncertainty
- If antibiotics given: doxycycline 200 mg stat then 100 mg OD for 5 days (first-line) or amoxicillin 500 mg TDS for 5 days
3
Safety netting
- Return if symptoms worsen, fever develops, breathlessness increases, or cough persists >3 weeks
- Persistent cough >3 weeks: investigate for pertussis, asthma, GORD, ACE inhibitor cough, or lung cancer
Complications
- Secondary bacterial pneumonia: If symptoms worsen or high fever develops
- Post-infectious cough: Persistent cough for weeks after acute infection — airway hyperreactivity
- Antibiotic-related side effects: Diarrhoea, C. difficile, allergic reactions — risks of unnecessary prescribing
UKMLA Exam Tips
- 1Acute bronchitis = cough + normal chest examination + no systemic toxicity = NO antibiotics
- 2Green/purulent sputum does NOT equal bacterial infection — it reflects neutrophil activity
- 3CRP point-of-care testing can help guide antibiotic decisions when uncertain
- 4Antibiotics reduce cough duration by <1 day in acute bronchitis — risks outweigh benefits in most cases
- 5If cough >3 weeks: investigate further (CXR, pertussis, spirometry)
- 6NICE NG120 is the key guideline — know the CRP thresholds for antibiotic decision-making
practicetest your knowledge on acute bronchitisApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — respiratory and beyond.
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