What is the differential diagnosis for a 16-year-old patient presenting with nausea, vomiting, cough, fever, and rhinorrhea?

Differential Diagnosis for a 16-Year-Old with Nausea, Vomiting, Cough, Fever, Congestion, and Rhinorrhea

The most likely diagnosis is viral upper respiratory infection (influenza or other respiratory virus), but you must actively rule out bacterial superinfection, particularly if symptoms persist beyond 7-10 days or worsen after initial improvement. 1, 2

Primary Differential Diagnoses

1. Viral Upper Respiratory Infection (Most Common)

• Influenza is the leading consideration given the constellation of fever, cough, rhinorrhea, and systemic symptoms (nausea/vomiting) in a 16-year-old 3, 4
• Influenza characteristically presents with abrupt onset of fever, myalgia, headache, severe malaise, nonproductive cough, sore throat, and rhinitis 3, 4
• Gastrointestinal symptoms (nausea, vomiting) occur commonly in children and adolescents with influenza, distinguishing it from typical adult presentations 3, 4
• Other viral causes include parainfluenza virus, rhinovirus, coronavirus, adenovirus, respiratory syncytial virus, and enteroviruses 3
• Uncomplicated viral illness typically resolves within 3-7 days, though cough can persist for more than 2 weeks 1, 4

2. Bacterial Superinfection (Critical to Identify)

You must suspect bacterial infection if any of these three criteria are met: 1

• Persistent symptoms ≥10 days without improvement (suggests acute bacterial rhinosinusitis) 1
• Worsening after initial improvement within the first 10 days (the "double-sickening" pattern) 1
• Severe symptoms at onset: fever ≥39°C with purulent nasal discharge during the first 3-4 days 1

3. Group A Streptococcal Pharyngitis

• Consider if sore throat is prominent, though the presence of cough, rhinorrhea, and congestion strongly suggests viral etiology rather than GAS 3
• GAS pharyngitis is primarily a disease of children 5-15 years of age, making this age group appropriate 3
• Clinical findings highly suggestive of viral origin include coryza, hoarseness, cough, and rhinorrhea—all present in this patient 3
• Nausea, vomiting, and abdominal pain can occur with GAS pharyngitis, but the respiratory symptoms make viral infection more likely 3

4. COVID-19

• Presents with similar symptoms: fever, cough, nasal congestion, rhinorrhea, and gastrointestinal symptoms (nausea, vomiting, diarrhea) 3
• Differential diagnosis includes other viral respiratory infections caused by influenza virus, parainfluenza virus, adenovirus, respiratory syncytial virus 3
• RT-PCR testing of throat swabs or nasopharyngeal samples confirms diagnosis 3

5. Avian Influenza (Low Probability Without Exposure)

• Only consider if there is exposure history to poultry or travel to endemic areas 3
• In adolescents (aged <16 years), avian influenza presents with fever (100%), cough (57-100%), rhinorrhea (43-57%), vomiting (29%), and diarrhea (14-57%) 3
• Associated with lymphopenia, deranged liver function tests, and high mortality (29-86% in hospitalized patients) 3

Critical Timeline for Decision-Making

Days 0-2: Expect fever and constitutional symptoms (headache, myalgias) to be most pronounced 1

Days 3-6: Respiratory symptoms (congestion, cough, rhinorrhea) become predominant as fever resolves 1

Days 3-7: Uncomplicated viral illness should be resolving 1, 4

Day 10 or beyond: Persistent symptoms without improvement mandate consideration of bacterial superinfection 1

Any time within first 10 days: Worsening after initial improvement indicates bacterial superinfection 1

Immediate Management Approach

Supportive Care (First-Line for Viral Infection)

• Antipyretics (acetaminophen or ibuprofen) for fever control; never aspirin in patients under 16 years due to Reye syndrome risk 2
• Ensure adequate hydration 2
• Small, frequent meals if nausea persists 5

When to Consider Antiviral Therapy

• If influenza is confirmed or highly suspected and patient presents within 48 hours of symptom onset 1
• Oseltamivir can be considered up to 6 days in high-risk patients 1

When to Initiate Antibiotics

If bacterial superinfection is suspected based on the three criteria above, start empiric antibiotics: 1

• Co-amoxiclav (amoxicillin-clavulanate) is first-line for patients under 12 years 1
• For adolescents ≥12 years, doxycycline is an alternative 1
• Coverage should include S. pneumoniae, S. aureus, and H. influenzae 1
• In penicillin allergy: clarithromycin or cefuroxime 1

Red Flags Requiring Urgent Evaluation

Immediately escalate care if any of these are present: 2

• Respiratory distress or cyanosis
• Altered consciousness or drowsiness
• Severe dehydration or inability to take oral fluids
• Fever persisting >4-5 days without improvement
• Extreme pallor or signs of septicemia

Common Pitfalls to Avoid

• Do not assume purulent nasal discharge alone indicates bacterial infection—this can occur several days into uncomplicated viral infections 1
• Do not prescribe antibiotics for uncomplicated viral URIs—they provide no benefit and increase resistance 2
• Do not rely on clinical symptoms alone to diagnose influenza—sensitivity is only 63-78% compared to viral culture 3, 4
• Do not order chest radiography in patients with normal vital signs and clear lung examination 2
• Do not use antihistamines or decongestants as primary treatment—insufficient evidence supports their use 2