Should a patient with influenza (flu) and hyperthermia be seen at the hospital?

Should a Fever of 105°F Be Seen at the Hospital with Flu?

Yes, a patient with influenza and a fever of 105°F (40.6°C) requires immediate hospital evaluation, as this degree of hyperthermia represents a clinical instability marker and is independently associated with increased mortality, ICU admission, and acute kidney injury. 1

Why This Fever Mandates Hospital Assessment

A temperature of 105°F (40.6°C) falls into the extreme hyperthermia category that research has shown carries significantly worse outcomes:

• Body temperature >39.7°C (103.5°F) is progressively associated with increased mortality (OR 1.64-2.22) compared to lower-grade fevers, and your patient exceeds this threshold. 1

• Temperatures >39.5°C (103.1°F) are independently associated with acute kidney injury (OR 1.48-2.91), and temperatures >39.7°C are progressively associated with increased ICU admission risk. 1

• Fever >37.8°C (100°F) is one of the clinical instability criteria that should prompt continued hospitalization or admission in influenza patients, and 105°F far exceeds this threshold. 2, 3

Clinical Instability Assessment

The patient should be evaluated for two or more of the following instability criteria, which would mandate hospital admission: 2, 4, 3

• Temperature >37.8°C (100°F) — clearly met at 105°F
• Heart rate >100/min
• Respiratory rate ≥24/min
• Systolic blood pressure <90 mmHg
• Oxygen saturation <90%
• Inability to maintain oral intake
• Abnormal mental status

Even one criterion (the extreme fever alone) warrants serious consideration for admission given the magnitude of temperature elevation. 1

Immediate Hospital Management Required

Antiviral Therapy

• Start oseltamivir 75 mg orally twice daily for 5 days immediately, even if the patient is beyond 48 hours of symptom onset, as severely ill hospitalized patients may benefit from late antiviral treatment. 2, 4

• Reduce dose to 75 mg once daily if creatinine clearance is <30 mL/min. 2, 4

Monitoring Protocol

• Monitor temperature, respiratory rate, pulse, blood pressure, mental status, and oxygen saturation at least twice daily, with more frequent monitoring given the severity of fever. 2, 4, 3

• Use an Early Warning Score system for systematic tracking. 2, 4

Supportive Care

• Assess for volume depletion and provide IV fluids as needed, as extreme hyperthermia increases insensible losses and risk of acute kidney injury. 2, 4, 1

• Provide oxygen therapy if hypoxic, targeting PaO2 >8 kPa and SpO2 ≥92%. 2, 4, 5

Antibiotic Coverage

• Consider empiric antibiotics for bacterial superinfection, particularly if the patient has worsening symptoms, respiratory distress, or is at high risk for complications. 2, 4

• First-line: Co-amoxiclav to cover Streptococcus pneumoniae, Staphylococcus aureus, and Haemophilus influenzae. 4

Critical Pitfalls to Avoid

• Do not manage this patient at home — temperatures >39.5°C are associated with adverse clinical outcomes and warrant aggressive evaluation and treatment. 1

• Do not delay hospital evaluation waiting to see if fever responds to antipyretics — the magnitude of fever itself is a risk marker independent of other symptoms. 1

• Do not withhold oseltamivir based on symptom duration in a severely ill patient with extreme hyperthermia, as hospitalized patients may benefit even beyond 48 hours. 2, 4

• Do not discharge until the patient is clinically stable with fewer than two instability criteria for at least 24 hours. 2, 4