What is the appropriate diagnosis and treatment for a fever lasting 2 days and a cough lasting 2 weeks?

Diagnosis and Management of Fever for 2 Days and Cough for 2 Weeks

Immediate Diagnostic Consideration

This presentation requires immediate evaluation for pertussis (whooping cough), which should be presumed present until proven otherwise, and empirical antibiotic treatment should be started immediately without waiting for laboratory confirmation. 1, 2

The 2-week duration of cough with new-onset fever is a critical diagnostic pattern. According to the American College of Chest Physicians, any cough lasting ≥2 weeks accompanied by paroxysmal episodes, post-tussive vomiting, or inspiratory whooping sound should be diagnosed as Bordetella pertussis infection unless another diagnosis is proven. 3 The recent addition of fever suggests either the catarrhal phase of pertussis or a secondary complication. 3

Initial Clinical Assessment

Evaluate for the following specific features:

• Paroxysmal coughing fits: Series of expiratory bursts followed by sudden loud inspiratory sound (though this "whoop" is frequently absent in adults). 3
• Post-tussive vomiting: Common in pertussis and highly suggestive of the diagnosis. 3
• Nocturnal worsening: Cough that intensifies at night or after cold air exposure. 3
• Vital sign abnormalities: Heart rate ≥100 beats/min, respiratory rate ≥24 breaths/min, or temperature ≥38°C warrant consideration of pneumonia. 3
• Chest examination findings: Focal consolidation (rales, egophony, fremitus) suggests pneumonia rather than pertussis or acute bronchitis. 3

Immediate Management Algorithm

Step 1: Start Empirical Antibiotic Treatment (Do Not Delay)

Azithromycin is the first-line treatment and should be initiated immediately upon clinical suspicion. 2, 4

• Adult dosing: 500 mg on day 1, then 250 mg daily on days 2-5. 4
• Early treatment within the first 2 weeks rapidly clears bacteria, reduces coughing paroxysms, and prevents complications. 2, 4
• Treatment after 2 weeks has limited clinical benefit for symptom reduction but remains indicated to prevent transmission. 2, 4

Alternative if azithromycin unavailable: Erythromycin 1-2 g/day in divided doses for 14 days (though inferior tolerability). 2, 4

Step 2: Implement Isolation Precautions

• Isolate the patient for 5 days from the start of antibiotic treatment to prevent disease spread. 3, 2, 4
• Without antibiotics, isolation must continue for 21 days after cough onset. 4
• Patient may return to work/school after completing 5 days of antibiotics. 4

Step 3: Obtain Diagnostic Confirmation (But Do Not Delay Treatment)

• Nasopharyngeal aspirate or Dacron swab for B. pertussis culture is the definitive diagnostic test. 3, 2, 4
• Bacterial isolation is the only certain way to confirm diagnosis, though sensitivity may be as low as 25-50%. 3
• PCR is not routinely recommended due to lack of universally validated technique. 3, 2
• Paired serology (IgG/IgA against pertussis toxin) showing 4-fold increase between acute and convalescent phases can provide presumptive diagnosis. 3, 2

Step 4: Rule Out Pneumonia

If vital signs are abnormal or focal chest findings are present, obtain chest radiography. 3 The absence of abnormal vital signs and focal consolidation on examination sufficiently reduces pneumonia likelihood that radiography is usually unnecessary. 3

Important: Purulent sputum does NOT indicate bacterial infection requiring antibiotics—it can result from viral infection or sloughed epithelial cells. 3

Symptomatic Management

For Cough Suppression

• First-line: Ipratropium inhalation to attenuate cough. 3, 1, 2
• Second-line: Dextromethorphan 60 mg (not over-the-counter doses, which are subtherapeutic) when other measures fail. 3, 1, 2
• For severe paroxysms: Prednisone 30-40 mg/day for a short, finite period after ruling out other common causes. 3, 1, 2

Avoid These Interventions

• Do NOT use antibiotics if pertussis is ruled out and no bacterial infection is confirmed—they provide no benefit for viral post-infectious cough. 3, 2
• Do NOT use long-acting β-agonists, antihistamines, or pertussis immunoglobulin—no evidence supports their benefit. 3

Differential Diagnoses to Consider

If Pertussis is Ruled Out:

• Post-infectious cough (3-8 weeks duration): Treat with ipratropium; consider inhaled corticosteroids if quality of life is affected and ipratropium fails. 3, 1
• Acute bronchitis: Most cases are viral; antibiotics are not indicated. 3
• Pneumonia: Requires chest radiography if vital signs abnormal or focal findings present. 3
• COVID-19 or other viral pneumonia: Consider if fever pattern and imaging suggest consolidation or ground-glass opacities. 3
• Influenza: If within 48 hours of symptom onset and influenza is circulating, consider oseltamivir. 5

Laboratory Testing

• White blood cell count: May be normal or decreased in viral infections; leukocytosis with lymphocytosis is typical of pertussis but frequently absent. 3
• Lymphocyte count: Absolute value <0.8 × 10⁹/L warrants rechecking in 3 days. 3

Critical Pitfalls to Avoid

1. Delaying pertussis treatment while waiting for laboratory confirmation decreases effectiveness. 2, 4 Treatment must begin immediately upon clinical suspicion.

2. Forgetting isolation precautions leads to transmission—patient is contagious until 5 days after starting antibiotics. 2, 4

3. Using antibiotics indiscriminately for viral post-infectious cough provides no benefit. 3, 2

4. Using subtherapeutic doses of cough suppressants—over-the-counter dextromethorphan is insufficient; 60 mg is needed for optimal effect. 1, 2

5. Misclassifying as chronic cough at 2 weeks—this is still acute/subacute phase with different management implications. 1, 2

When to Reassess or Escalate

• Immediate escalation needed if: Hemoptysis, constitutional symptoms beyond fever, respiratory distress, or hypoxemia develop. 1
• At 3 weeks: If cough persists, consider post-infectious cough and trial ipratropium. 1
• At 8 weeks: If cough persists, evaluate as chronic cough with full workup including consideration of asthma, gastroesophageal reflux disease, and upper airway cough syndrome. 3, 1