Bronchitis — Causes, Symptoms, Diagnosis & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Bronchitis is inflammation of the mucous membranes lining the bronchi — the airways conducting air from the trachea to the alveoli. It presents in two distinct clinical forms. Acute bronchitis is a self-limiting inflammation of the lower respiratory airways, lasting 1-3 weeks and caused predominantly by respiratory viruses (in 90% of cases). It is one of the most common conditions in primary care, affecting approximately 5% of adults annually, and is unfortunately among the most common reasons for inappropriate antibiotic prescribing globally. Chronic bronchitis is defined clinically as productive cough with sputum production on most days for at least 3 months in two consecutive years, in the absence of another explanation. It is the dominant component of chronic obstructive pulmonary disease (COPD) and is fundamentally a smoking-related disease characterised by mucous gland hypertrophy, goblet cell metaplasia, and impaired mucociliary clearance. The distinction between the two forms is critical — acute bronchitis is treated with symptom relief, not antibiotics; chronic bronchitis requires long-term management of underlying COPD.

Acute bronchitis: caused by respiratory viruses in approximately 90% of cases — rhinovirus, adenovirus, coronavirus, influenza, parainfluenza, RSV, and human metapneumovirus. Bacterial causes (Mycoplasma pneumoniae, Bordetella pertussis, Chlamydophila pneumoniae) account for approximately 5-10% — clinically distinguishable by prolonged paroxysmal cough (pertussis), atypical features, or lack of improvement. Precipitating factors: preceding upper respiratory tract infection, cold and damp weather, air pollution, and immunocompromise. Chronic bronchitis/COPD: cigarette smoking is the overwhelmingly dominant cause (15-20 pack-year history increases COPD risk 5-fold). Other risk factors include occupational dust and chemical exposures (coal dust, grain dust, silica, cadmium), biomass fuel smoke (major cause in low-income countries — cooking fires), air pollution, recurrent childhood respiratory infections, alpha-1 antitrypsin deficiency (genetic cause of early-onset emphysema — affects 1-3% of COPD patients), and airway hyperresponsiveness.

Acute bronchitis: characteristic productive cough — initially dry, then progressing to clear, yellow, or green sputum (sputum colour does NOT reliably indicate bacterial infection — purulent sputum can occur in viral bronchitis due to inflammatory cell shedding). Cough typically lasts 3 weeks on average (range 1-6 weeks). Associated symptoms: mild sore throat, runny nose, low-grade fever, malaise, and wheeze or dyspnoea if airway hyperreactivity is present. Severe or prolonged cough with inspiratory whoop and post-tussive vomiting suggests pertussis ('whooping cough'). Haemoptysis (blood in sputum), high fever, unilateral chest signs, or dyspnoea disproportionate to the cough suggest pneumonia — requires imaging. Chronic bronchitis: daily productive cough for months to years; gradually increasing dyspnoea on exertion; exercise intolerance; recurrent 'chest infections' (COPD exacerbations); wheeze; and the eventual development of respiratory failure in advanced disease. Acute exacerbations of chronic bronchitis (AECB) produce worsening dyspnoea, increased sputum volume and purulence, and may precipitate respiratory failure — particularly dangerous in patients with significantly reduced baseline lung function.

Acute bronchitis is a clinical diagnosis — based on symptoms and examination findings. Investigations are not routinely required in otherwise healthy adults. Chest X-ray is NOT indicated unless pneumonia is suspected (fever above 38°C, unilateral signs, rapidly worsening dyspnoea, or high clinical suspicion from CRP above 20 mg/L combined with abnormal chest signs). Point-of-care CRP testing (below 20 mg/L makes bacterial infection very unlikely; above 100 mg/L suggests pneumonia) can guide antibiotic prescribing decisions. Sputum culture: generally unhelpful in acute bronchitis — viral and bacterial causes cannot be reliably distinguished, and culture results take days. Pertussis: PCR from nasopharyngeal swab (most sensitive in first 3 weeks of illness). Chronic bronchitis/COPD diagnosis: spirometry is mandatory — FEV1/FVC ratio below 0.70 post-bronchodilator confirms obstructive airflow limitation. MRC dyspnoea scale and COPD assessment test (CAT score) assess symptom burden. HRCT thorax identifies emphysema and bronchial wall thickening pattern. FBC (polycythaemia in hypoxic COPD), alpha-1 antitrypsin level in young patients or non-smokers.

Acute bronchitis treatment: the cornerstone is reassurance and symptom management — antibiotics do NOT reduce duration or severity of acute bronchitis and should NOT be routinely prescribed. Evidence-based symptomatic treatments: honey (1-2 teaspoons — superior to placebo for cough in adults and children over 12 months); paracetamol or ibuprofen for fever and discomfort; adequate hydration to loosen secretions; and steam inhalation or cool air humidifier. Over-the-counter cough suppressants (dextromethorphan, pholcodine) and expectorants (guaifenesin) have limited evidence but are widely used for symptom relief. Salbutamol inhaler (SABA) may reduce cough duration in patients with underlying airway hyperreactivity. Antibiotics are indicated ONLY for: confirmed or strongly suspected pertussis (azithromycin 500 mg day 1 then 250 mg days 2-5 — reduces infectivity but not duration if started after 3 weeks); pneumonia; or severely immunocompromised patients. Chronic bronchitis/COPD management: smoking cessation is the most effective intervention. Short-acting bronchodilators (SABAs — salbutamol; SAMAs — ipratropium) for acute relief. Long-acting bronchodilators (LABAs — salmeterol, formoterol; LAMAs — tiotropium, umeclidinium) for maintenance. ICS/LABA combinations for moderate-to-severe COPD with frequent exacerbations. Pulmonary rehabilitation. Long-term oxygen therapy (LTOT) for resting hypoxaemia (PaO2 below 7.3 kPa). AECB: prednisolone 30 mg for 5 days; antibiotics (amoxicillin, doxycycline, or co-amoxiclav) only if clinical signs of bacterial exacerbation.

Acute bronchitis, while usually self-limiting, can lead to complications in vulnerable patients. Pneumonia: the most significant acute complication — bacterial superinfection of already-inflamed airways causes consolidation; risk is highest in the elderly, smokers, immunocompromised individuals, and those with COPD; diagnosed by high fever, focal chest signs, and chest X-ray consolidation. Acute exacerbation of COPD (AECB): in patients with pre-existing COPD, acute bronchitis precipitates severe AECB requiring hospitalisation, IV bronchodilators, corticosteroids, and sometimes NIV ventilation. Type 2 respiratory failure: severe AECB causes hypercapnia (elevated pCO2) and hypoxaemia — potentially fatal without ventilatory support. Post-infectious airway hyperreactivity: up to 40% of patients develop reactive airway disease following acute viral bronchitis — causing cough and wheeze for weeks to months after the infection clears, resembling asthma. Chronic bronchitis progression: in smokers, recurrent bronchitis episodes accelerate airway remodelling and can evolve into COPD over years. Cor pulmonale (right heart failure from chronic hypoxaemia) is a late complication of chronic bronchitis/COPD.

Acute bronchitis prevention: annual influenza vaccination reduces the incidence of influenza-related bronchitis — recommended for all adults over 65, those with chronic conditions, and healthcare workers. COVID-19 and RSV vaccination also reduces respiratory illness burden. Good hand hygiene (hand washing for 20 seconds with soap and water, particularly before meals and after public transport) is the most effective measure for preventing viral respiratory infections. Avoid close contact with symptomatic individuals when possible. Chronic bronchitis prevention: smoking cessation is the single most important preventable intervention — even long-term smokers who quit reduce their rate of FEV1 decline to that of non-smokers within years, and risk of COPD exacerbations falls substantially. Avoid occupational dust and chemical exposures; use appropriate respiratory protective equipment. Reduce indoor biomass fuel combustion. Pneumococcal vaccination (PCV20 and PPV23) reduces hospitalisation from bacterial pneumonia in COPD patients. Pulmonary rehabilitation after each AECB hospitalisation reduces readmission rates.

Seek emergency care (call 999/911) for acute bronchitis symptoms accompanied by: severe breathlessness at rest or rapid deterioration; oxygen saturation below 92% on pulse oximeter; bluish discolouration of lips or fingertips (cyanosis); altered consciousness or confusion; severe chest pain; or inability to speak more than a few words. See a GP urgently (same-day or next day) for: high fever above 38.5°C persisting more than 3-4 days; coughing up blood (haemoptysis); rapidly worsening breathlessness over 24-48 hours; unwell elderly or immunocompromised patients; and COPD patients with significantly increased breathlessness, sputum volume or purulence beyond baseline (COPD exacerbation). Patients with chronic bronchitis/COPD should have a written exacerbation action plan specifying when to start rescue prednisolone and antibiotics and when to seek emergency care.