Acute Bronchitis
Why most cases clear up without antibiotics
Acute bronchitis is a self-limiting inflammation of the bronchi (the large airways of the lung), most commonly caused by a viral infection. It is one of the most common conditions seen in primary care, accounting for around 5% of GP consultations each year. Despite widespread public expectation, antibiotics are not required for the vast majority of cases.
What is Acute Bronchitis?
Acute bronchitis is an inflammatory condition of the bronchial tubes — the large airways connecting the windpipe (trachea) to the lungs — usually lasting 1 to 3 weeks. The inflammation causes increased mucus production and a protective cough reflex. It is distinct from pneumonia (which involves the lung tissue itself) and from chronic bronchitis (which is defined by a productive cough on most days for at least 3 months per year for 2 consecutive years and is part of COPD). Most cases of acute bronchitis are self-limiting and resolve completely without complications.
Causes
Viral infections account for approximately 90% of acute bronchitis cases. The most common causative viruses include rhinovirus (most prevalent), influenza A and B, RSV (respiratory syncytial virus), coronavirus, adenovirus and parainfluenza virus. Bacterial causes — Mycoplasma pneumoniae, Bordetella pertussis (whooping cough), Chlamydophila pneumoniae — account for fewer than 10% of cases. Bacterial bronchitis may be suspected if symptoms are particularly severe or prolonged (>3 weeks), or in specific epidemiological contexts (e.g., pertussis outbreaks). Environmental irritants such as air pollution, dust and tobacco smoke can also trigger or exacerbate bronchitis.
Symptoms
The predominant symptom of acute bronchitis is cough — which may initially be dry then becomes productive of yellow, green or clear sputum. Importantly, coloured sputum does not indicate bacterial infection and does not warrant antibiotics. Associated symptoms include retrosternal (behind the breastbone) discomfort or tightness, mild wheeze or breathlessness, mild fever (usually <38.5°C), and symptoms of an upper respiratory tract infection (runny nose, sore throat, mild myalgia). Symptoms typically peak at days 3–5 and resolve within 2–3 weeks, although cough can persist for up to 3 weeks or occasionally longer. Patients should be advised that a post-infectious cough of 3–4 weeks is normal.
When Antibiotics are NOT Needed
NICE NG120 (Antimicrobial Prescribing for Acute Bronchitis) clearly states that antibiotics should NOT be prescribed routinely for acute bronchitis in otherwise healthy adults, as the condition is predominantly viral and self-limiting. Evidence consistently shows that antibiotics reduce the duration of illness by less than half a day on average while causing significant risks of side effects (diarrhoea, nausea, rashes, Clostridioides difficile infection) and contributing to antimicrobial resistance. Sputum colour (clear vs coloured) is NOT a reliable indicator of bacterial infection and should not guide antibiotic decisions. The prescribing decision should be guided by clinical features — particularly whether the patient has signs of pneumonia, is severely unwell, or has significant comorbidities.
Management
Management of acute bronchitis is supportive. NICE NG120 recommends: adequate oral hydration (at least 8 glasses of water per day), paracetamol or ibuprofen for fever and chest discomfort, honey and lemon in warm water to soothe cough (honey should not be given to children under 1 year due to risk of infant botulism), and rest. Over-the-counter cough remedies have limited evidence but may be tried for short-term symptom relief. A delayed prescribing strategy can be used for patients who are particularly anxious — a prescription is issued but patients are advised to collect it only if symptoms worsen or fail to improve after 14 days. This approach respects patient concern while reducing actual antibiotic consumption. Steam inhalation or nebulised saline may provide symptomatic relief. Patients with underlying asthma or COPD who develop wheeze during bronchitis should use their reliever inhaler as needed.
When to See a Doctor
Patients should seek medical review if: symptoms worsen significantly after initial improvement (suggesting secondary bacterial infection or pneumonia), cough persists beyond 3 weeks without improvement, they develop a high fever (>38.5°C), breathlessness at rest or reduced oxygen saturations, they cough up blood (haemoptysis), or they have significant comorbidities such as heart failure, COPD, diabetes, or immunosuppression. Signs of pneumonia — fever, productive cough, pleuritic chest pain, confusion, or rapid breathing — require chest X-ray and consideration of antibiotics. Elderly patients, young children, and those who are immunocompromised should have a lower threshold for medical review. If Bordetella pertussis (whooping cough) is suspected, azithromycin 500 mg OD for 3 days is recommended and contact tracing is required.