What is the cause of a persistent cough lasting 6 weeks in a patient after traveling to a new location?

Cough for 6 Weeks After Travel

The most likely diagnosis is postinfectious cough following a respiratory infection acquired during travel, and you should start with inhaled ipratropium bromide as first-line therapy after ruling out tuberculosis and pertussis. 1

Immediate Risk Stratification

At 6 weeks duration, this is a subacute cough (defined as 3-8 weeks), which sits at the critical transition point before becoming chronic. 1

Red Flags Requiring Urgent Evaluation

Check immediately for these concerning features that demand chest radiography and broader workup: 2, 3

• Hemoptysis (any amount)
• Vital sign abnormalities: heart rate ≥100 bpm, respiratory rate ≥24 breaths/min, temperature ≥38°C
• Systemic symptoms: fever, night sweats, unintentional weight loss
• Asymmetrical lung sounds or focal consolidation on examination
• Voice changes or hoarseness

If any red flags are present, obtain chest X-ray immediately before proceeding with empiric treatment. 2, 3

Critical Travel-Related Consideration: Tuberculosis

Given the travel history, tuberculosis must be actively excluded before assuming benign postinfectious cough. 1

When to Suspect TB

Screen for TB if the patient traveled to high-prevalence areas (sub-Saharan Africa, Southeast Asia, Eastern Europe, Latin America) or has: 1

• Cough ≥2 weeks in high-prevalence settings
• Systemic symptoms (fever, night sweats, weight loss)
• Known TB exposure during travel
• Immunocompromised status

TB Diagnostic Workup

If TB risk factors are present: 1

• Obtain chest radiograph looking for upper lobe infiltrates, cavitation, or lymphadenopathy
• Collect three sputum specimens for acid-fast bacilli smear and culture
• Consider tuberculin skin test or interferon-gamma release assay

In high TB prevalence areas, cough ≥2 weeks warrants screening even without other symptoms, as 10-13% of such patients have smear-positive pulmonary TB. 1

Second Critical Diagnosis: Pertussis

Before treating as simple postinfectious cough, actively evaluate for pertussis, especially given potential exposure during travel. 1, 3

Pertussis Clinical Features

Suspect pertussis if the patient reports: 1, 3

• Paroxysmal coughing episodes (sudden, uncontrollable coughing fits)
• Post-tussive vomiting (vomiting triggered by cough)
• Inspiratory whooping sound after coughing paroxysms
• Known exposure to confirmed pertussis case

Pertussis Diagnostic Testing

If pertussis is suspected: 1, 3

• Obtain nasopharyngeal aspirate or Dacron swab for culture (gold standard)
• Order paired acute and convalescent sera for fourfold increase in IgG or IgA antibodies to pertussis toxin
• Start macrolide antibiotic immediately without waiting for confirmation if clinical suspicion is high

Early treatment within the first few weeks diminishes coughing paroxysms and prevents transmission. 1, 3

Medication Review

Stop any ACE inhibitor immediately if the patient is taking one. 2, 4

ACE inhibitors cause persistent cough, and the median time to resolution after discontinuation is 26 days—which could explain ongoing symptoms even if the medication preceded travel. 2, 4

Most Likely Diagnosis: Postinfectious Cough

If TB and pertussis are excluded and no red flags are present, postinfectious cough is the most common cause of subacute cough, accounting for approximately 48% of cases. 1, 2

Pathophysiology

Multiple mechanisms contribute: 1

• Postviral airway inflammation
• Bronchial hyperresponsiveness
• Mucus hypersecretion and impaired mucociliary clearance
• Upper airway cough syndrome (postnasal drip)
• Transient asthma-like features

First-Line Treatment Algorithm

Step 1: Inhaled Ipratropium Bromide

Prescribe inhaled ipratropium bromide as the only evidence-based first-line therapy for postinfectious cough. 1, 2

• Approximately 70% response rate with Grade B evidence
• Typical dosing: 2-4 puffs (18-36 mcg) four times daily
• Trial for 2 weeks before escalating therapy

Do NOT prescribe antibiotics—they have no role in postinfectious cough as the cause is not bacterial infection. 1, 2

Step 2: If Ipratropium Fails After 2 Weeks

Add inhaled corticosteroids if cough adversely affects quality of life and persists despite ipratropium. 1

• Use moderate-to-high dose inhaled corticosteroid
• Continue for 2-4 weeks

Step 3: For Severe Paroxysms

Consider prednisone 30-40 mg daily for a short, finite period (5-7 days) only if: 1

• Cough is severely affecting quality of life
• Other common causes (upper airway cough syndrome, asthma, GERD) have been ruled out
• Ipratropium and inhaled corticosteroids have failed

Step 4: Central Antitussives as Last Resort

Consider codeine or dextromethorphan only when other measures fail. 1

Alternative Diagnoses if Treatment Fails

If the patient does not respond to ipratropium within 2 weeks, consider these alternative diagnoses that can masquerade as postinfectious cough: 2, 4

Upper Airway Cough Syndrome (UACS)

• Trial first-generation antihistamine-decongestant combination for 1-2 weeks
• Look for postnasal drip, throat clearing, nasal congestion

Asthma or Cough-Variant Asthma

• Perform spirometry with bronchodilator response
• Consider methacholine challenge testing if spirometry is normal
• Trial inhaled bronchodilators and corticosteroids

Gastroesophageal Reflux Disease (GERD)

• Initiate high-dose PPI therapy for at least 8 weeks
• Note: Acid suppression alone is no longer recommended as sole therapy; comprehensive GERD management is required 4

Nonasthmatic Eosinophilic Bronchitis (NAEB)

• Consider sputum eosinophil count or induced sputum analysis
• Trial inhaled corticosteroids if eosinophilia is present

Critical Timeline: The 8-Week Threshold

If cough persists beyond 8 weeks despite appropriate treatment, it transitions to chronic cough and requires full chronic cough workup. 1, 2

At that point, consider: 2

• High-resolution CT chest
• 24-hour esophageal pH monitoring
• Bronchoscopy
• Referral to specialized cough clinic

Common Pitfalls to Avoid

1. Do NOT prescribe antibiotics for postinfectious cough unless pertussis is confirmed or bacterial sinusitis is documented. 1, 2

2. Do NOT assume "just bronchitis" without excluding TB in a traveler, especially from high-prevalence areas. 1

3. Do NOT wait beyond 8 weeks to escalate evaluation if cough persists despite treatment. 1, 2

4. Do NOT ignore medication review—ACE inhibitors must be stopped before pursuing extensive workup. 2, 4

5. Do NOT use codeine or dextromethorphan as first-line therapy—they should only be considered when other measures fail. 1

Follow-Up Strategy

Schedule follow-up in 4-6 weeks to reassess if cough persists. 2

Use a validated cough severity or quality of life tool to objectively assess treatment response rather than relying solely on subjective reporting. 2