In a healthy 35‑year‑old woman with a one‑week progressive upper‑respiratory illness (initial congestion, sore throat, cough) now presenting with myalgias, back pain, marked fatigue, nausea and vomiting, afebrile and with a normal chest X‑ray, what is the most likely diagnosis and appropriate outpatient management?

Clinical Diagnosis: Influenza or Post-Infectious Cough

This patient most likely has influenza or is in the early post-infectious phase of a viral upper respiratory infection, and should receive supportive care with guaifenesin, reassurance, and close follow-up—antibiotics are explicitly contraindicated.

Diagnostic Reasoning

Influenza Fits the Clinical Picture

The presentation strongly suggests influenza based on guideline-defined criteria:

• Acute illness with fever (though absent today, likely resolved), together with myalgia, cough, and sore throat meets the European guideline definition of influenza 1.
• The progression from upper respiratory symptoms (congestion, sore throat, cough) to systemic symptoms (myalgias, back pain, marked fatigue, nausea/vomiting) over one week mirrors the typical influenza timeline 1.
• Significant fatigue and myalgias are hallmark constitutional symptoms that distinguish influenza from simple acute bronchitis 1.

Pneumonia is Effectively Ruled Out

• Normal chest X-ray excludes community-acquired pneumonia, which would require cough plus either new focal chest signs, fever >4 days, or dyspnea/tachypnea 1.
• The patient is afebrile in clinic today, further reducing pneumonia probability 1.
• No focal chest signs (crackles, consolidation, egophony) on examination make pneumonia unlikely 2.

Post-Infectious Cough is the Alternative Diagnosis

If influenza testing is negative or unavailable, this presentation is consistent with post-infectious cough:

• Timeline of initial URI symptoms followed by persistent cough for 7 days fits the American Thoracic Society definition 3.
• Non-purulent sputum, no fever today, clear lungs exclude bacterial superinfection 3.
• The nausea and vomiting may reflect severe cough paroxysms or viral gastroenteritis, both common in post-viral states 3.

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Management Algorithm

Step 1: Supportive Care (First-Line)

Initiate symptomatic treatment immediately:

• Guaifenesin 200–400 mg every 4 hours (up to 6 times daily) to help loosen phlegm and make cough more productive 3.
• Adequate hydration, rest, warm facial packs, steamy showers, and sleeping with head elevated provide additional symptomatic relief 3.
• Reassure the patient that post-viral symptoms typically resolve within 10–14 days and that antibiotics are not indicated 3.

Step 2: Consider Antiviral Therapy (If Within 48 Hours of Symptom Onset)

Oseltamivir (Tamiflu) 75 mg twice daily for 5 days should be considered only if:

• Symptom onset was within the past 48 hours (this patient is at day 7, so oseltamivir is NOT indicated) 1, 4.
• Influenza is confirmed or highly suspected during community circulation 1.
• The patient is at high risk for complications (this patient is healthy, so risk is low) 1.

In this case, the window for oseltamivir has closed 1, 4.

Step 3: Escalate to Inhaled Ipratropium if Symptoms Persist (Second-Line)

If cough persists or worsens after 1–2 weeks and significantly affects quality of life:

• Inhaled ipratropium bromide 2–3 puffs (17–34 mcg per puff) four times daily has the strongest evidence for attenuating post-infectious cough 3.
• Expect clinical improvement within 1–2 weeks 3.

Step 4: Add Inhaled Corticosteroids if Ipratropium Fails (Third-Line)

If cough persists despite ipratropium and quality of life remains impaired:

• Fluticasone 220 mcg or budesonide 360 mcg twice daily may be added 3.
• Allow up to 8 weeks for full therapeutic response 3.

Step 5: Reserve Oral Prednisone for Severe Cases Only (Fourth-Line)

Prednisone 30–40 mg daily for 5–10 days should be prescribed only if:

• Severe cough paroxysms significantly impair quality of life and
• Upper airway cough syndrome, asthma, and GERD have been ruled out or adequately treated 3.

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What NOT to Do: Critical Pitfalls

Antibiotics Are Explicitly Contraindicated

• Antibiotics have no role in post-infectious cough or uncomplicated influenza because the cause is not bacterial infection 3, 2.
• Prescribing antibiotics provides no clinical benefit, contributes to antimicrobial resistance, and adds adverse-effect risk 3.
• Exceptions permitting antibiotics include confirmed bacterial sinusitis or early pertussis infection (neither is present here) 3.

Do Not Jump to Prednisone

• Prednisone should not be used for mild post-infectious cough; it is reserved for severe cases that have failed ipratropium and inhaled corticosteroids 3.

Do Not Overlook Red Flags

Instruct the patient to return immediately if:

• Fever develops or recurs (suggests bacterial superinfection or alternative diagnosis) 3.
• Hemoptysis occurs (requires urgent re-evaluation) 3.
• Symptoms worsen or fail to improve within 3–5 days (reassess for pneumonia, pertussis, or other diagnoses) 3.

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Follow-Up and Timeline Expectations

• Reassess within 3–5 days if symptoms do not improve or worsen 3.
• Acute post-viral symptoms generally respond to supportive care within 10–14 days 3.
• If cough persists beyond 8 weeks, reclassify as chronic cough and systematically evaluate for upper airway cough syndrome, asthma, and GERD 3.

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Special Considerations

Pertussis Must Be Excluded

• Pertussis should be suspected if cough lasts ≥2 weeks with paroxysms, post-tussive vomiting, or inspiratory "whoop" 3.
• If pertussis is confirmed, early macrolide therapy (azithromycin or clarithromycin) is indicated 3.

Asthma and GERD Are Common Mimics

• Cough-variant asthma accounts for 24–32% of chronic cough cases and may present without wheezing 3.
• "Silent GERD" frequently presents with cough as the sole manifestation, even without typical GI symptoms 3.
• If cough persists beyond 8 weeks, systematically evaluate for these conditions 3.