What are the treatment options for influenza?

Treatment of Influenza

Antiviral Therapy

Start oseltamivir 75 mg orally twice daily for 5 days as soon as possible for patients who are hospitalized, have severe/complicated illness, or are at high risk for complications, regardless of symptom duration. 1

Indications for Antiviral Treatment

Offer treatment immediately to: 1

• Any patient hospitalized with presumed influenza 1
• Patients with severe, complicated, or progressive illness 1
• All high-risk patients (children <2 years, adults ≥65 years, pregnant women, immunocompromised, chronic cardiac/pulmonary disease, morbidly obese with BMI ≥40) 1

Consider treatment for: 1

• Previously healthy outpatients if treatment can start within 48 hours of symptom onset 1
• Healthy children living with high-risk household contacts (infants <6 months or those with medical conditions predisposing to complications) 1

Timing and Efficacy

• The 48-hour window applies primarily to otherwise healthy adults—hospitalized and high-risk patients benefit from oseltamivir even when started >48 hours after symptom onset 1, 2, 3
• Treatment reduces illness duration by approximately 1-1.3 days in healthy adults and children 4, 5
• Early treatment reduces complications including otitis media in children and lower respiratory tract complications requiring antibiotics in adults 6
• Observational studies suggest reduced mortality in hospitalized patients treated with neuraminidase inhibitors 6

Dosing

Adults and children >40 kg: 75 mg orally twice daily for 5 days 1, 7, 4

Pediatric dosing (≥12 months): 7

• ≤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 adjustment: If creatinine clearance <30 mL/min, reduce to 75 mg once daily 2, 7

Infants <12 months: The AAP supports oseltamivir use from birth (including preterm infants) despite FDA approval only for ≥2 weeks of age, as benefits outweigh risks 1

Alternative Neuraminidase Inhibitor

Zanamivir (inhaled): 10 mg (two 5-mg inhalations) twice daily for 5 days 8

• Active against both influenza A and B 1, 8
• Contraindicated in patients with underlying airways disease (asthma, COPD) due to risk of serious bronchospasm 1, 8
• Approved for treatment in patients ≥7 years 1, 8
• Alternative for patients unable to take oseltamivir 3

Agents NOT Recommended

• Amantadine and rimantadine: Only active against influenza A (not B), widespread resistance, no longer recommended 1, 5, 9
• Double-dose oseltamivir: Randomized trial showed no benefit over standard dosing 1

Antibiotic Management

Do NOT routinely prescribe antibiotics for uncomplicated influenza—it is a viral illness. 2, 3, 7

When to Add Antibiotics

Add antibiotics immediately if any of the following develop: 2, 3

• Worsening symptoms after initial improvement (recrudescent fever) 2, 3
• New or worsening dyspnea or shortness of breath 2
• Productive cough with purulent sputum 2
• Focal chest findings on examination 2
• Radiographic evidence of pneumonia 2, 3

Antibiotic Selection Based on Severity

Non-severe bacterial pneumonia (CURB-65 0-2): 2, 3

• First-line: Co-amoxiclav (amoxicillin-clavulanate) orally 2, 3
• Alternatives: Doxycycline or respiratory fluoroquinolone 2

Severe pneumonia (CURB-65 ≥3 or bilateral infiltrates): 2, 3

• Immediate IV combination therapy: Co-amoxiclav OR 2nd/3rd generation cephalosporin (cefuroxime, cefotaxime) PLUS macrolide (clarithromycin) 2, 3
• Administer within 4 hours of admission 2, 3

Antibiotic Duration

• 7 days: Non-severe, uncomplicated pneumonia 2, 3
• 10 days: Severe pneumonia without identified pathogen 2, 3
• 14-21 days: Confirmed or suspected S. aureus or Gram-negative pneumonia 2, 3

IV to Oral Switch

Switch from IV to oral antibiotics when: 3

• Clinical improvement occurs
• Temperature normal for 24 hours
• No contraindication to oral route

Supportive Care

• Antipyretics: Acetaminophen or ibuprofen for fever control (preferred in elderly) 2, 3
• Aspirin is absolutely contraindicated in children <16 years due to Reye's syndrome risk 3
• Hydration: Ensure adequate oral fluids or IV fluids if unable to maintain oral intake 2, 3
• Oxygen: Provide supplemental oxygen to maintain SpO2 >92% 2

Red Flags Requiring Immediate Re-evaluation

Instruct patients to return immediately if: 2, 3

• Shortness of breath at rest develops
• Painful or difficult breathing occurs
• Bloody sputum appears
• Fever returns after initial improvement (recrudescent fever)
• Dyspnea worsens
• Mental status changes
• Inability to maintain oral intake

Special Populations

Elderly patients (≥65 years): 2

• Automatically high-risk regardless of comorbidities
• May not mount adequate febrile response but still require treatment based on clinical presentation and positive testing
• Consider longer treatment courses if severely immunocompromised, though not routinely necessary

Children <2 years: At increased risk of hospitalization and complications; treat aggressively 1

Pregnant women: High-risk population; treat with oseltamivir regardless of timing 1

Common Pitfalls

• Do not delay oseltamivir while awaiting confirmatory testing—start empirically based on clinical judgment during influenza season 1
• Do not withhold oseltamivir from high-risk or hospitalized patients presenting >48 hours after symptom onset—they still benefit 1, 2, 3
• Do not prescribe antibiotics reflexively for influenza—reserve for documented or highly suspected bacterial superinfection 2, 3, 7
• Vomiting is the most common adverse effect of oseltamivir (15% vs 9% placebo)—not a reason to discontinue in most cases 1