Post COVID Cough

Post COVID cough is cough that begins during, or after, COVID-19 infection and persists for more than 3 weeks (subacute), or more than 8 weeks (chronic), with no alternative explanation after assessment. It is part of the wider post-COVID condition, and affects about 2 to 20% of patients at 8 to 12 weeks after infection, with a lower rate with newer variants and vaccination.

• Mechanisms: viral damage to the airway epithelium, neurogenic inflammation, and cough hypersensitivity through sensitisation of vagal sensory neurones. Other contributing mechanisms are postnasal drip from rhinitis or sinusitis, airway hyperresponsiveness or new asthma, gastro oesophageal reflux, persistent lung injury (organising pneumonia, fibrosis), laryngeal sensory neuropathy, anxiety and dysfunctional breathing, and deconditioning.
• Risk factors: severe acute illness (hospital or intensive care admission), female sex, middle age (35 to 65 years), smoking, asthma or other chronic lung disease, obesity, and multiple comorbidities.
• Most patients improve gradually, and about 90% have improved by 12 weeks. A smaller group has a persistent cough lasting many months, which may reflect a cough hypersensitivity syndrome.
• Cough is often accompanied by fatigue, breathlessness, chest tightness, throat irritation, loss or distortion of smell, brain fog and sleep disturbance.

• A dry or slightly productive cough, often a tickle in the throat, triggered by talking, laughing, cold air, strong smells, eating and exercise, worse at night or on waking. Many patients have hoarseness, throat clearing, a sense of postnasal drip, and chest tightness.
• Other features: breathlessness on exertion, fatigue, palpitations, and symptoms of reflux. Complications such as urinary incontinence, cough syncope, rib pain and sleep disturbance may occur.
• Examination: normal in most patients. Look for hypoxia on exertion, wheeze, crackles, clubbing, signs of heart failure, and nasal and throat disease.
• Differential diagnosis: upper airway cough syndrome, asthma (including new post-viral asthma and cough variant asthma), gastro oesophageal reflux, pneumonia (organising pneumonia, post-COVID fibrosis and bronchiectasis), pulmonary embolism, pulmonary hypertension, heart failure, tuberculosis, lung cancer, ACE inhibitor cough, vocal cord dysfunction, dysfunctional breathing, and pertussis.
• Red flags: haemoptysis, weight loss, night sweats, fever, progressive breathlessness, resting hypoxia or desaturation on exertion (a fall of 4% or more, or below 92%), chest pain, unilateral leg swelling, clubbing, hoarseness for more than 3 weeks, immunosuppression, and abnormal chest signs.
• Complications: sleep loss, rib fracture, urinary incontinence, syncope, anxiety and depression, reduced work capacity, and prolonged symptoms.

• Clinical, with a structured assessment of cough lasting more than 3 weeks after an infection, and exclusion of serious causes. Document the date of infection, severity and treatment, the cough pattern and triggers, associated symptoms, vaccination, smoking, medicines (ACE inhibitors), and previous lung disease.
• Examine: oxygen saturation at rest and after exertion (a 1 minute sit-to-stand test, or 3 to 6 minutes of walking), pulse, blood pressure, chest, heart, legs, nose and throat, and measure body mass index.
• Tests for cough present beyond 3 weeks:
  • Chest X-ray in all patients.
  • Spirometry with bronchodilator reversibility (forced expiratory volume in 1 second increase of 12% and 200 mL or more), and peak flow variability (above 20% over 2 weeks).
  • Fractional exhaled nitric oxide (above 40 ppb suggests eosinophilic airway inflammation).
  • Full blood count with eosinophil count, C-reactive protein, ferritin, thyroid function tests, and glucose.
  • Electrocardiogram, and B-type natriuretic peptide if heart failure is suspected.
• Further tests if abnormal findings or symptoms persist beyond 8 to 12 weeks: high resolution CT of the chest (organising pneumonia, fibrosis, bronchiectasis), full lung function with diffusing capacity, exercise testing, echocardiography, CT pulmonary angiography when embolism is suspected, laryngoscopy for voice change or throat symptoms, and a sputum test for tuberculosis when risk exists.
• Screen for upper airway disease, reflux, asthma, anxiety, depression and sleep disorders, and measure the impact of the cough using a validated cough score or a 0 to 10 scale.

• Explain that the cough is common, usually improves with time, and is not contagious after the acute infection. Advise avoiding smoking, irritants, and cold dry air, and give self-care advice (warm drinks, honey 5 to 10 mL at night for adults, lozenges, sipping water instead of throat clearing, and a humidifier).
• Treat the likely contributors with a time limited course of each, and review the response:
  • Upper airway cough syndrome: fluticasone propionate nasal spray 50 micrograms per spray, 2 sprays into each nostril once daily (or mometasone 50 micrograms per spray, 2 sprays into each nostril once daily), saline irrigation twice daily, and azelastine 137 micrograms per spray, 1 spray into each nostril twice daily, for 2 to 4 weeks. A first generation antihistamine such as chlorphenamine 4 mg orally every 4 to 6 hours at night (maximum 24 mg per day) for 1 to 2 weeks, with caution about drowsiness.
  • Asthma, cough variant asthma and airway inflammation: inhaled corticosteroid such as beclometasone 200 to 400 micrograms twice daily, or budesonide 200 to 400 micrograms twice daily, for 4 to 8 weeks, with a spacer, and salbutamol 100 micrograms, 2 puffs as needed. Add formoterol 12 micrograms twice daily (as a combination inhaler) when asthma is confirmed. A short course of prednisolone 30 to 40 mg orally once daily for 5 to 7 days is used for severe or disabling post-infectious cough after other causes are excluded (specialist guided, evidence limited). Montelukast 10 mg once daily at night is an alternative.
  • Reflux: omeprazole 20 to 40 mg once daily 30 minutes before breakfast for 8 weeks, with an alginate (sodium alginate and potassium bicarbonate 10 to 20 mL after meals and at bedtime), and dietary and weight advice. Stop if there is no benefit.
  • Organising pneumonia: prednisolone 0.5 to 1 mg/kg orally once daily (typically 30 to 40 mg) for 4 to 6 weeks, then tapered over 3 to 6 months under specialist care, with bone and gastric protection (calcium and vitamin D, omeprazole 20 mg daily), and monitoring of glucose.
  • Persistent pulmonary fibrosis: refer to an interstitial lung disease specialist for antifibrotic and supportive care.
• Cough suppression: dextromethorphan 10 to 20 mg orally every 4 to 6 hours (maximum 120 mg per day) at night for up to 1 to 2 weeks, or codeine linctus 15 to 30 mg orally every 6 hours (maximum 120 mg per day) for a few days. Avoid in respiratory depression, pregnancy and breastfeeding (codeine), and in those using serotonergic antidepressants (dextromethorphan).
• Refractory cough (after thorough assessment and treatment of other causes):
  • Speech and language therapy (cough suppression therapy, education, vocal hygiene, and breathing control, 4 to 6 sessions), which reduces cough in about 30 to 50% of patients, and is the first line non-drug option.
  • Gabapentin 100 mg orally at night, increased every 3 to 7 days to 300 mg 3 times daily, and, if tolerated, to a maximum of 1800 mg per day in divided doses, for 8 to 12 weeks (off label), reducing the dose in renal impairment. Drowsiness, dizziness and confusion are common. Pregabalin 25 to 75 mg twice daily is an alternative.
  • Low dose slow release morphine 5 mg orally 12 hourly, increased to 10 mg 12 hourly after 1 week, in specialist care for severe disabling cough, with laxatives and monitoring.
  • Amitriptyline 10 mg orally at night, increased by 10 mg every 1 to 2 weeks to 25 to 50 mg, in specialist care.
• Pulmonary rehabilitation, graded exercise, and breathing retraining (diaphragmatic breathing, slow nasal breathing) for breathlessness, fatigue and deconditioning. Avoid pushing exercise beyond tolerance in patients with post-exertional symptom worsening.
• Treat anxiety, depression and sleep disturbance: cognitive behavioural therapy, and sertraline 25 to 50 mg daily where indicated.
• Special groups:
  • Children: post-infectious cough usually settles in 4 to 8 weeks. Avoid cough suppressants, treat asthma and nasal disease, and refer for cough beyond 4 weeks (chest X-ray, spirometry, asthma assessment, tuberculosis contact). Consider protracted bacterial bronchitis, treated with amoxicillin clavulanate 22.5 mg/kg of amoxicillin orally 12 hourly for 2 weeks.
  • Pregnancy: use honey, saline, fluticasone or budesonide nasal sprays, and inhaled asthma treatment. Avoid codeine, gabapentin and montelukast unless benefits outweigh risks. Omeprazole is acceptable when needed.
  • Elderly: investigate for heart failure, pneumonia and cancer, review polypharmacy, and use lower doses of gabapentin and amitriptyline.
  • Smokers: strongly advise cessation, with nicotine patch 21 mg per 24 hours (more than 10 cigarettes daily) and varenicline 0.5 mg daily for 3 days, then 0.5 mg twice daily for 4 days, then 1 mg twice daily for 12 weeks.
  • Renal impairment: reduce gabapentin and pregabalin doses, and avoid NSAIDs.
  • Immunosuppressed: lower threshold for CT imaging, and exclude opportunistic infection and tuberculosis.
• Follow up: review at 4 to 6 weeks after each treatment step. Refer to a respiratory or cough clinic for persistent cough beyond 8 to 12 weeks despite assessment and treatment, abnormal imaging, hypoxia, or red flags, and refer urgently for haemoptysis, suspected cancer, or progressive breathlessness.