What is the recommended treatment for viral influenza?

Treatment of Viral Influenza

Start antiviral treatment immediately with oral oseltamivir (75 mg twice daily for 5 days in adults) for any patient hospitalized with influenza, those with severe/progressive illness, high-risk patients (including children <2 years, adults ≥65 years, pregnant women, immunocompromised, and those with chronic conditions), regardless of symptom duration or vaccination status. 1

Who Must Receive Antiviral Treatment

Treatment should be initiated as soon as possible—ideally within 48 hours of symptom onset—but do not withhold antivirals in severely ill or hospitalized patients even if >48 hours have passed, as treatment still reduces morbidity and mortality 1, 2.

Mandatory treatment groups include:

• Any hospitalized patient with documented or suspected influenza 1, 2
• Patients with severe, complicated, or progressive illness of any duration 1, 2
• All high-risk patients: children <2 years, adults ≥65 years 1
• Pregnant women and those within 2 weeks postpartum 1
• Immunocompromised patients 1, 2
• Patients with chronic medical conditions (pulmonary, cardiovascular, renal, metabolic, diabetes, hemoglobinopathies) 1

Optional treatment:

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

First-Line Antiviral: Oseltamivir

Oseltamivir is the drug of choice for influenza treatment 1, 3.

Adult dosing: 75 mg orally twice daily for 5 days 1, 4

Pediatric dosing (weight-based for children ≥1 year): 1, 4

• ≤15 kg: 30 mg twice daily
• 15.1-23 kg: 45 mg twice daily
• 23.1-40 kg: 60 mg twice daily

• 40 kg: 75 mg twice daily

Infants <1 year: 1, 4

• 9-11 months: 3.5 mg/kg per dose twice daily
• 0-8 months: 3 mg/kg per dose twice daily

Oseltamivir may be taken with or without food, though administration with meals improves gastrointestinal tolerability 4.

Alternative Antivirals

Zanamivir (inhaled) is an equally acceptable alternative for patients without chronic respiratory disease (asthma, COPD), as it carries risk of serious bronchospasm in these populations 1, 3, 5.

• Adult/pediatric dosing (≥7 years): 10 mg (two 5-mg inhalations) twice daily for 5 days 1, 5
• Zanamivir is more difficult to administer than oseltamivir 1
• Do not use in hospitalized patients or those with underlying airways disease 3, 5

Peramivir (intravenous) is useful for patients unable to absorb oral medications or tolerate inhaled therapy 3.

• Approved for acute uncomplicated influenza in patients ≥2 years symptomatic ≤2 days 3
• Single intravenous dose option available 1

Baloxavir marboxil (oral) is a newer cap-dependent endonuclease inhibitor with different mechanism than neuraminidase inhibitors 3.

• Approved for uncomplicated influenza in patients ≥12 years symptomatic ≤48 hours 3
• Conditionally recommended by WHO for non-severe influenza in high-risk patients 6

Critical Treatment Modifications

Extended duration therapy: Consider treatment >5 days for immunocompromised patients or those with severe lower respiratory tract disease (pneumonia, ARDS), as viral replication is often protracted 1.

Do NOT use:

• Amantadine or rimantadine due to high resistance rates among circulating influenza A viruses 1, 2
• Combination neuraminidase inhibitors 1
• Routine higher doses of FDA-approved antivirals 1

Managing Bacterial Coinfection

Empirically treat bacterial coinfection in addition to antiviral therapy when patients: 1, 2

• Present initially with severe disease (extensive pneumonia, respiratory failure, hypotension, persistent fever)
• Deteriorate after initial improvement, particularly those on antivirals
• Fail to improve after 3-5 days of antiviral treatment

The IDSA strongly recommends investigating and treating bacterial coinfection in these scenarios, as bacterial superinfection significantly increases mortality 1.

Resistance Monitoring

Resistance testing should be considered for: 1

• Patients developing laboratory-confirmed influenza while on or immediately after neuraminidase inhibitor prophylaxis
• Immunocompromised patients with persistent viral replication (>7-10 days by RT-PCR or culture) who remain ill during/after treatment

During recent influenza seasons, the vast majority of strains have been susceptible to oseltamivir, zanamivir, and peramivir 1. Continuous CDC surveillance monitors resistance patterns 1, 3.

Common Pitfalls to Avoid

Do not delay treatment waiting for test results—start empiric antivirals immediately in high-risk or severely ill patients when influenza is circulating in the community 1, 2.

Do not withhold antivirals beyond 48 hours in hospitalized or severely ill patients, as benefit persists even with delayed initiation 1, 2.

Do not use corticosteroids as adjunctive therapy for seasonal influenza treatment 2.

Do not use zanamivir in patients with asthma or COPD due to bronchospasm risk 3, 5.

Investigate alternative diagnoses in patients who fail to improve or deteriorate despite appropriate antiviral treatment 1.