What is the most likely diagnosis and management for a 27-year-old female with a 7-day history of productive cough and negative influenza (flu) test results?

Most Likely Diagnosis and Management

This 27-year-old female with a 7-day productive cough and negative influenza test most likely has acute bronchitis from a viral lower respiratory tract infection, and should be managed with supportive care using first-generation antihistamine-decongestant combinations rather than antibiotics. 1

Diagnostic Approach

Acute cough is defined as lasting less than 3 weeks, and at 7 days, this patient falls squarely in the acute category. 1 The key initial step is determining whether this represents a serious illness requiring urgent intervention versus a self-limited viral process. 1

Rule Out Life-Threatening Conditions First

• Assess for pneumonia by examining for fever, tachypnea, focal lung findings, crackles, or asymmetric breath sounds—if present, obtain chest radiography. 1
• Consider pulmonary embolism if there are risk factors, pleuritic chest pain, or hemoptysis. 1
• Evaluate for pertussis if cough has paroxysmal quality, post-tussive vomiting, or inspiratory whooping sound, especially if duration extends beyond 2 weeks. 2, 3

Most Likely Diagnosis: Acute Viral Bronchitis

When patients present with productive cough in the acute phase, acute bronchitis from viral lower respiratory tract infection should be the primary consideration. 1 This is particularly likely given:

• Negative influenza test rules out influenza A as the specific viral etiology. 1, 4
• Productive cough without fever, purulent sputum, or lung crackles in an otherwise healthy nonsmoker strongly suggests viral rather than bacterial infection. 2
• Duration of 7 days is typical for acute viral bronchitis, which causes cough lasting 1-3 weeks. 5, 6

Management Algorithm

First-Line Treatment: Symptomatic Relief

The most effective treatment for acute viral cough is a first-generation antihistamine plus decongestant combination. 1, 6 This approach has been proven in double-blind placebo-controlled studies to decrease cough severity and hasten resolution. 1

• Prescribe brompheniramine/pseudoephedrine or chlorpheniramine/phenylephrine taken regularly, not as needed. 2, 7
• Alternative supportive measures include guaifenesin 200-400 mg every 4 hours (up to 6 times daily) to help loosen phlegm, honey and lemon for symptomatic relief, adequate hydration, and rest. 2

What NOT to Do: Antibiotics Are Contraindicated

Antibiotics are explicitly contraindicated for acute viral bronchitis and provide no benefit. 2, 7 The American College of Chest Physicians strongly recommends against antibiotic use unless there is clear evidence of bacterial infection such as:

• Bacterial sinusitis with purulent nasal discharge, facial pain, and prolonged symptoms. 2, 3
• Early pertussis infection confirmed by nasopharyngeal culture, in which case macrolide antibiotics (azithromycin or erythromycin) should be started immediately. 7, 3, 5
• Pneumonia confirmed by chest radiography showing infiltrates. 1, 5

Prescribing antibiotics for viral bronchitis contributes to antimicrobial resistance, causes adverse effects including allergic reactions and C. difficile infection, and wastes healthcare resources. 7, 5

Common Pitfalls to Avoid

• Do not interpret colored or green sputum as indicating bacterial infection—most short-term coughs produce colored phlegm even when viral in origin. 2
• Do not use nasal decongestant sprays for more than 3-5 days due to rebound congestion risk. 7
• Do not assume the cough will resolve immediately—viral bronchitis typically causes cough lasting 1-3 weeks, so symptoms at day 7 are expected. 5, 6

Red Flags Requiring Re-Evaluation

Instruct the patient to return immediately if any of the following develop: 2, 7

• Fever (suggests bacterial superinfection or pneumonia)
• Hemoptysis (requires chest radiography and broader differential)
• Worsening dyspnea or tachypnea (suggests pneumonia or other serious pathology)
• Symptoms persisting beyond 3 weeks (transitions to subacute cough requiring different evaluation)

If Cough Persists Beyond 3 Weeks

If cough extends to 3-8 weeks (subacute cough), consider postinfectious cough and treat with inhaled ipratropium bromide 2-3 puffs four times daily, which has the strongest evidence for attenuating postinfectious cough. 2, 7, 3

If cough persists beyond 8 weeks (chronic cough), systematically evaluate for the three most common causes: 1, 2

• Upper airway cough syndrome (UACS) from chronic rhinosinusitis—treat with first-generation antihistamine-decongestant plus intranasal corticosteroid. 2, 7
• Asthma or non-asthmatic eosinophilic bronchitis—consider bronchoprovocation testing or empiric trial of inhaled corticosteroids. 1, 2
• Gastroesophageal reflux disease (GERD)—initiate high-dose PPI therapy (omeprazole 40 mg twice daily) even without typical GI symptoms. 2, 7