What is the recommended treatment for influenza?

Treatment of Influenza

For patients with suspected or confirmed influenza, initiate neuraminidase inhibitor therapy immediately—particularly oseltamivir—for all hospitalized patients, those with severe/progressive illness, and high-risk individuals, ideally within 48 hours of symptom onset but even beyond this window for severe cases. 1, 2

Who Should Receive Antiviral Treatment

Mandatory Treatment Groups

Treatment should be started as soon as possible for:

• Any hospitalized patient with suspected or confirmed influenza, regardless of symptom duration or vaccination status 3, 1, 4
• Severe, complicated, or progressive illness attributable to influenza in any patient 3, 1
• High-risk patients including:
  • Children <2 years (especially <6 months who have highest mortality) 3, 2
  • Adults ≥65 years 3, 2
  • Pregnant and postpartum women (within 2 weeks of delivery) 3, 2
  • Immunocompromised individuals 3, 2
  • Chronic medical conditions (pulmonary, cardiovascular, renal, hepatic, hematologic, metabolic, neurologic) 3, 2
  • Morbid obesity (BMI ≥40) 3
  • Nursing home residents 3

Consider Treatment For

• Previously healthy outpatients with suspected influenza if treatment can start within 48 hours of symptom onset 1, 2
• Healthy children whose household contacts are <6 months old or have high-risk conditions 3, 4

First-Line Antiviral Medications

Oseltamivir (Preferred Agent)

Dosing for treatment:

• Adults and adolescents ≥13 years: 75 mg orally twice daily for 5 days 5, 2
• Children 1-12 years (weight-based):
  • ≤15 kg: 30 mg twice daily 5, 4
  • 15.1-23 kg: 45 mg twice daily 5, 4
  • 23.1-40 kg: 60 mg twice daily 5, 4

  • 40 kg: 75 mg twice daily 5, 4

• Infants 2 weeks to <1 year: 3 mg/kg twice daily 5, 4

Key advantages: Available as oral suspension (6 mg/mL), can be taken with or without food (though food improves tolerability), most extensively studied in children 4, 5

Alternative Neuraminidase Inhibitors

• Zanamivir: 10 mg (two 5-mg inhalations) twice daily for 5 days in patients ≥7 years 6
  • Contraindicated in patients with airway disease (asthma, COPD) due to bronchospasm risk 2, 6
• Peramivir: Intravenous option for patients ≥2 years who cannot take oral/inhaled medications 4

Do not use standard doses higher than FDA-approved; double-dose oseltamivir showed no benefit over standard dosing 3, 1

Critical Timing Considerations

Treatment is most effective when started within 48 hours of symptom onset, reducing illness duration by approximately 24-36 hours and decreasing complications by 34% in children 3, 4, 7

However, do not withhold treatment beyond 48 hours for:

• Hospitalized patients (treat even if >48 hours from onset) 3, 1
• Patients with severe or progressive disease 3, 1
• High-risk patients with worsening symptoms 1, 2

Start treatment immediately without waiting for laboratory confirmation when influenza is clinically suspected during flu season 3, 1, 4

Diagnostic Testing Approach

• RT-PCR or molecular assays are preferred for hospitalized patients due to superior sensitivity 1
• Multiplex RT-PCR panels should be used in immunocompromised patients 1
• Rapid antigen tests should not be used in hospitalized patients except when molecular assays unavailable; negative results require RT-PCR confirmation 1, 4
• Never delay treatment while awaiting test results if clinical suspicion is high 3, 1, 4

Management of Bacterial Complications

When to Add Antibiotics

Investigate and empirically treat bacterial coinfection if:

• Severe initial presentation 1
• Clinical deterioration after initial improvement 1
• Failure to improve after 3-5 days of antiviral treatment 1
• Worsening symptoms with recrudescent fever or increasing dyspnea 3

Antibiotic Selection

For non-severe influenza-related pneumonia:

• Oral co-amoxiclav or tetracycline as first-line 3, 1
• Macrolide (clarithromycin) or fluoroquinolone as alternatives 3

For severe influenza-related pneumonia:

• Immediate parenteral therapy with broad-spectrum β-lactamase stable antibiotic (co-amoxiclav or cefuroxime/cefotaxime) PLUS macrolide (clarithromycin or erythromycin) 3, 1
• Target likely pathogens: S. pneumoniae, S. aureus (including MRSA), S. pyogenes 3
• Administer within 4 hours of admission 3

Do not routinely use antibiotics for uncomplicated influenza or acute bronchitis without pneumonia in previously healthy adults 3, 2

Special Populations

Renal Impairment

Reduce oseltamivir dose by half (75 mg once daily) for creatinine clearance <30 mL/min 2, 5

Immunocompromised Patients

• Consider longer treatment duration beyond standard 5 days 1
• Monitor for antiviral resistance, especially with persistent viral replication 1
• Prophylaxis may be extended up to 12 weeks 5

Pregnant Women

Treat with oseltamivir immediately; pregnancy increases risk of severe complications and mortality 3, 2

What NOT to Do

Avoid the following unless specifically indicated for other reasons:

• Corticosteroids for influenza treatment 1, 2
• Immunoglobulin preparations for seasonal influenza 1
• Amantadine/rimantadine due to high resistance rates 4
• Antibiotics for uncomplicated influenza without bacterial coinfection 3, 2

Common Pitfalls

• Most common error: Failing to treat high-risk outpatients empirically within 48 hours 8
• Antibiotic overuse: 30% of influenza patients receive unnecessary antibiotics 8
• Delayed treatment: Only 15-19% of eligible high-risk patients receive timely antivirals 8
• Vomiting with oseltamivir: Occurs in ~15% of children; taking with food reduces this side effect 3, 4

Monitoring for Antiviral Resistance

Watch for resistance in:

• Patients developing influenza while on/immediately after prophylaxis 1
• Immunocompromised patients with persistent viral replication 1
• Patients with severe influenza not improving with treatment 1

Current surveillance shows most circulating strains remain susceptible to oseltamivir, zanamivir, and peramivir 4