Postviral Cough

Postviral cough is cough that continues for 3 to 8 weeks after an acute viral respiratory infection, in a patient with a normal chest X-ray and examination, and no other cause. It affects about 11 to 25% of people after a viral infection, commonly after influenza, parainfluenza, respiratory syncytial virus, rhinovirus, adenovirus and coronaviruses, and may also follow bronchiolitis in infants.

• Mechanism: viral injury to the airway epithelium, with loss of ciliated cells, mucus hypersecretion, neurogenic inflammation, increased sensitivity of the cough reflex (through release of tachykinins and activation of sensory nerve endings), and transient airway hyperresponsiveness. Postnasal drip and reflux may add to the cough.
• It is usually self-limiting, with cough settling within 8 weeks in over 90% of cases, and quicker in children. Persistent cough beyond 8 weeks requires a search for other causes, such as asthma, upper airway cough syndrome, reflux, pertussis, tuberculosis or cancer.
• Factors predisposing to prolonged cough: smoking, atopy, asthma, older age, female sex, chronic obstructive pulmonary disease, a severe initial illness, and pertussis.
• Postviral cough is a diagnosis of exclusion: the history of a preceding viral illness, a gradual improvement, and a normal examination and chest X-ray.

• A dry, irritating, tickly cough following an upper respiratory tract infection, with improvement of fever, nasal congestion and sore throat but persistent cough, worse in the evening and at night, with talking, laughing, cold air and exercise. Occasional wheeze, chest tightness and a sore throat from coughing.
• Normal examination, with normal vital signs, and no focal chest signs. Occasionally there is a transient wheeze, or throat redness.
• Hoarseness, a sore throat, postnasal drip and mild chest soreness from coughing may be present. There is no fever, weight loss, haemoptysis or breathlessness at rest.
• Differential diagnosis: asthma and cough variant asthma, upper airway cough syndrome, pertussis, gastro oesophageal reflux, pneumonia, tuberculosis, lung cancer, heart failure, ACE inhibitor cough, bronchiectasis and post-COVID syndromes.
• Red flags: haemoptysis, weight loss, night sweats, breathlessness at rest, fever, chest pain, hoarseness lasting more than 3 weeks in a smoker, clubbing, abnormal chest signs, and immunosuppression.
• Complications: sleep disturbance, rib fracture, cough syncope, urinary incontinence, hoarseness, anxiety, and, in some cases, development of asthma or chronic cough.

• Clinical. Record the preceding illness (onset date, symptoms, treatment), smoking, medicines, contact with pertussis or tuberculosis, and associated symptoms of asthma, rhinitis and reflux. Examine for oxygen saturation, chest signs and throat.
• A chest X-ray is indicated when the cough has lasted 3 weeks or more, to exclude pneumonia, tuberculosis and cancer. It is normal in postviral cough.
• Spirometry with reversibility testing (forced expiratory volume in 1 second increase of 12% and 200 mL or more), or peak flow variability above 20% over 2 weeks, when wheeze or asthma is suspected. Spirometry is usually normal, and mild transient reversibility may occur.
• Test for pertussis (polymerase chain reaction or serology) if there is paroxysmal cough, post-tussive vomiting, a whoop, or exposure.
• Sputum tests for tuberculosis in people with risk factors, weight loss or night sweats, and in high prevalence settings.
• Further investigation (CT of the chest, bronchoscopy, laryngoscopy) is reserved for abnormal findings, red flags, or persistence for more than 8 weeks.

• Reassure that the cough is common and resolves, usually within 8 weeks, and that antibiotics do not help. Advise against smoking and exposure to irritants.
• Supportive measures: warm fluids, honey (2.5 to 5 mL at bedtime, not for under 1 year), lozenges, humidified air, and avoiding repeated throat clearing. Reduce triggers, such as cold air and strong smells, and use a scarf over the mouth in cold weather.
• Treatment of dominant mechanisms where evident, with review at 2 to 4 weeks:
  • Dry irritating cough: 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. Codeine linctus 15 to 30 mg orally every 6 hours (maximum 120 mg per day) for a few days in adults, avoiding driving and alcohol. Avoid codeine in children under 12 years, in pregnancy, in breastfeeding, and in respiratory depression.
  • Nasal symptoms or postnasal drip: fluticasone propionate nasal spray 50 micrograms per spray, 2 sprays into each nostril once daily, saline irrigation, and chlorphenamine 4 mg orally every 4 to 6 hours at night for 1 to 2 weeks (maximum 24 mg per day).
  • Wheeze, chest tightness or airway hyperresponsiveness: inhaled salbutamol 100 micrograms, 2 puffs via a spacer 4 to 6 hourly as needed for 1 to 2 weeks, with ipratropium bromide 20 to 40 micrograms (1 to 2 puffs) 3 to 4 times daily as an alternative for cough after infection.
  • Persistent, disabling cough after infection: inhaled corticosteroid such as beclometasone 200 to 400 micrograms twice daily, or budesonide 200 to 400 micrograms twice daily, for 2 to 4 weeks, to reduce airway inflammation and cough reflex sensitivity. For severe paroxysms, prednisolone 30 to 40 mg orally once daily for 5 to 7 days after excluding infection and when no contraindication (specialist guided, evidence limited).
  • Reflux symptoms: omeprazole 20 mg once daily before breakfast for 4 to 8 weeks, and advice on diet and head elevation.
• Pertussis or a household outbreak: give treatment for pertussis if suspected within 3 weeks of cough onset, with azithromycin 500 mg orally on day 1, then 250 mg daily for 4 days (child 10 mg/kg once daily for 5 days), because it reduces spread. After this window, only supportive therapy is useful.
• Avoid unnecessary antibiotics, over-the-counter cough and cold remedies in young children, and repeated courses of oral steroids.
• Special groups:
  • Children: expect cough to last 2 to 4 weeks. Use honey for those over 1 year, treat nasal symptoms, and avoid cough medicines in children under 6 years (and codeine under 12 years). Assess for asthma and protracted bacterial bronchitis if cough lasts more than 4 weeks, and consider amoxicillin clavulanate 22.5 mg/kg of amoxicillin orally 12 hourly for 2 weeks for a persistent wet cough.
  • Pregnancy: use honey, saline, nasal steroids and, if needed, salbutamol. Avoid codeine and dextromethorphan unless advised.
  • Elderly: investigate more readily for pneumonia, heart failure and cancer, and take care with sedating drugs.
  • Smokers: offer cessation support, nicotine replacement and varenicline, and note that cough may persist for months in smokers.
  • Asthma and COPD: stepped treatment, with review of inhaler technique.
• Follow up: review at 3 to 4 weeks. If cough persists beyond 8 weeks, or if red flags occur, arrange a full assessment for chronic cough and refer to a respiratory specialist.