What is the appropriate treatment for a 19-year-old male with a positive Flu A test result, presenting with symptoms of vomiting, diarrhea, body aches, headache, and cough, following exposure to COVID-19?

Treatment of Influenza A in a 19-Year-Old Male with COVID-19 Exposure

Primary Recommendation

Initiate oseltamivir (Tamiflu) 75 mg orally twice daily for 5 days immediately, as the patient tested positive for Influenza A and presents within 48 hours of symptom onset. 1, 2

Treatment Rationale and Algorithm

Antiviral Therapy for Confirmed Influenza A

• Oseltamivir should be started as soon as possible from first appearance of flu symptoms, ideally within 48 hours of onset 1, 2
• The greatest benefit occurs when antiviral therapy is initiated within 24 hours of symptom onset, reducing illness duration by approximately 24 hours in otherwise healthy patients 2
• This 19-year-old male with symptom onset "yesterday evening" (approximately 12-24 hours ago) is well within the therapeutic window 1
• The standard adult dose is 75 mg orally twice daily for 5 days, which matches the prescribed regimen 1

COVID-19 Coinfection Considerations

• Despite COVID-19 exposure, the positive Flu A test and negative COVID-19 test indicate isolated influenza infection at this time 3, 4
• COVID-19 and influenza coinfection is rare (0.54% in one series of 1,103 COVID-19 patients), and when it occurs, coinfection may actually alleviate inflammation in certain populations compared to COVID-19 alone 3, 4
• The patient's clinical presentation (vomiting, diarrhea, body aches, headache, cough with low-grade fever) is consistent with influenza with gastrointestinal manifestations 1, 2
• Continue monitoring for development of COVID-19 symptoms over the next 7-14 days given documented exposure 5

Supportive Care Management

Symptomatic Treatment

• Use acetaminophen (paracetamol) as first-line antipyretic rather than ibuprofen when viral illness is confirmed 6
• Administer 500-1000 mg orally every 4-6 hours as needed for fever >38.5°C (maximum 4 grams/24 hours) 6
• The prescribed ibuprofen PRN is acceptable but acetaminophen is preferred for viral illness 6

Hydration and Nutrition

• Increase fluid intake to prevent dehydration, but limit to no more than 2 liters per day 6
• Target energy intake of 25-30 kcal/kg/day with protein-rich foods (eggs, fish, lean meat, dairy) and carbohydrates 6
• Bland diet is appropriate for managing gastrointestinal symptoms 6

Activity and Isolation

• Bed rest with avoidance of overexertion during acute illness 6
• Self-quarantine until symptoms resolve to prevent transmission 6
• Regular sleep schedule, avoidance of alcohol and smoking 6

Red Flag Symptoms Requiring Immediate Re-evaluation

Respiratory Deterioration

• Respiratory rate ≥30 breaths/minute 6
• Development of dyspnea or shortness of breath 6
• Chest pain or pressure 6
• Oxygen saturation decline (though currently 98% on room air) 6

Systemic Warning Signs

• Persistent high fever despite antipyretics 6
• Altered mental status or severe headache 6, 7
• Inability to maintain oral hydration 6
• Worsening symptoms after initial improvement 6

COVID-19 Development

• New loss of taste or smell (anosmia/ageusia) 5
• Progressive symptoms beyond typical influenza course (5-7 days) 5
• Development of isolated GI symptoms may precede COVID-19 respiratory symptoms by a few days in high prevalence settings 5

Common Pitfalls to Avoid

Diagnostic Considerations

• Do not dismiss the possibility of subsequent COVID-19 infection despite negative initial test 5
• GI symptoms (nausea, vomiting, diarrhea) are associated with 70% increased risk of COVID-19 positivity (adjusted OR 1.7; 95% CI 1.1-2.5) 5
• In high COVID-19 prevalence settings, consider repeat testing if symptoms persist or worsen beyond typical influenza course 5

Treatment Timing

• Do not delay oseltamivir initiation while awaiting additional testing or symptom evolution 1, 2
• Efficacy decreases significantly after 48 hours from symptom onset 2
• The patient should take missed doses as soon as remembered, except if within 2 hours of next scheduled dose 1

Vaccination Considerations

• Oseltamivir is not a substitute for annual influenza vaccination 1
• Avoid administration of live attenuated influenza vaccine (LAIV) within 2 weeks before or 48 hours after oseltamivir administration 1
• Continue annual flu vaccination according to immunization practice guidelines 1

Follow-Up Protocol

• Return immediately if any red flag symptoms develop 6
• Routine follow-up if symptoms do not improve within 3-5 days of antiviral therapy 2
• Monitor for development of COVID-19 symptoms over 14 days post-exposure 5
• Consider repeat COVID-19 testing if respiratory symptoms worsen or new symptoms develop 5