What is the treatment for a patient with influenza A?

Treatment of Influenza A

Start antiviral treatment immediately with oseltamivir 75 mg orally twice daily for 5 days as soon as influenza A is suspected or confirmed, regardless of symptom duration in high-risk patients or those with severe disease. 1

Who Should Receive Antiviral Treatment

Mandatory Treatment Groups (Start Immediately)

• All hospitalized patients with suspected or confirmed influenza, regardless of illness duration prior to hospitalization 1
• Outpatients with severe or progressive illness, regardless of illness duration 1
• High-risk patients including:
  • Children younger than 2 years and adults ≥65 years 1
  • Pregnant women and those within 2 weeks postpartum 1
  • Patients with chronic medical conditions (pulmonary, cardiovascular, renal, hepatic, hematologic, metabolic, or neurologic disorders) 1
  • Immunocompromised patients 1

Optional Treatment Groups

• Otherwise healthy outpatients not at high risk may be considered for treatment if presenting within 48 hours of symptom onset 1

First-Line Antiviral Therapy

Oseltamivir (Preferred Agent)

• Adult dosing: 75 mg orally twice daily for 5 days 1, 2
• Pediatric dosing (weight-based): 3, 2
  • ≤15 kg: 30 mg twice daily

  • 15-23 kg: 45 mg twice daily

  • 23-40 kg: 60 mg twice daily

  • 40 kg: 75 mg twice daily

• Renal impairment: Reduce to 75 mg once daily if creatinine clearance <30 mL/min 4, 2
• Tolerability: Take with food to reduce nausea and vomiting (occurs in 10-15% of patients) 3, 5

Alternative Neuraminidase Inhibitors

• Zanamivir (inhaled): 10 mg (two 5-mg inhalations) twice daily for 5 days for ages ≥7 years 1, 6
  • Contraindication: Not recommended for patients with underlying airways disease (asthma, COPD) due to risk of serious bronchospasm 6
• Peramivir (IV): Single dose option or for severely ill patients with concerns about oral absorption 1, 3

Agents NOT Recommended

• Do not use amantadine or rimantadine due to high resistance rates among current influenza A strains 3
• Do not use combination neuraminidase inhibitors 1

Timing of Treatment Initiation

Critical principle: Earlier treatment provides greater benefit, but do not withhold treatment based on time from symptom onset in high-risk or severely ill patients. 1

• Optimal window: Within 12 hours of fever onset reduces illness duration by 3.1 days (41% reduction) 7
• Standard window: Within 48 hours provides approximately 24-hour reduction in illness duration 3, 5, 8
• Beyond 48 hours: Still treat hospitalized patients, severely ill patients, and immunocompromised patients regardless of symptom duration 1, 9

Extended Treatment Duration

Consider longer than 5-day treatment courses for: 1, 9

• Immunocompromised patients with evidence of persistent viral replication
• Patients requiring hospitalization for severe lower respiratory tract disease (pneumonia or ARDS)
• Patients with persistent fever after 6 days of standard treatment 9

Management of Bacterial Coinfection

When to Suspect and Treat Bacterial Coinfection

• Immediate empiric antibiotics (in addition to antivirals) for patients presenting with: 1
  • Extensive pneumonia
  • Respiratory failure
  • Hypotension and fever
• Investigate and treat patients who deteriorate after initial improvement 1
• Consider investigation in patients who fail to improve after 3-5 days of antiviral treatment 1

Antibiotic Selection

• Non-severe pneumonia: Oral co-amoxiclav or tetracycline 1
• Severe pneumonia: IV combination therapy with broad-spectrum β-lactamase stable antibiotic (co-amoxiclav or 2nd/3rd generation cephalosporin) plus macrolide (clarithromycin or erythromycin) 1
• Alternative: Fluoroquinolone with enhanced pneumococcal activity (levofloxacin or moxifloxacin) 1

Resistance Testing Considerations

Consider neuraminidase inhibitor resistance testing for: 1

• Patients who develop influenza while on or immediately after prophylaxis
• Immunocompromised patients with persistent viral replication (>7-10 days) who remain ill during treatment
• Patients with severe influenza who fail to improve with evidence of persistent viral replication
• Patients who inadvertently received subtherapeutic dosing

What NOT to Do

• Do not use corticosteroids as adjunctive therapy unless clinically indicated for other reasons 1
• Do not routinely use higher doses of FDA-approved neuraminidase inhibitors 1
• Do not use intravenous immunoglobulin routinely for treatment 1

Common Pitfalls to Avoid

• Delaying treatment while awaiting laboratory confirmation—treat empirically based on clinical presentation 1
• Withholding treatment in elderly or immunocompromised patients who lack documented fever—they may still benefit 1, 4
• Stopping investigation if patient fails to improve on antivirals—investigate other causes and bacterial coinfection 1
• Forgetting dose adjustment in renal impairment—reduces risk of adverse effects 4, 2