What is the treatment for influenza?

Treatment of Influenza

Oral oseltamivir 75 mg twice daily for 5 days is the first-line antiviral treatment for influenza and should be initiated as soon as possible, ideally within 48 hours of symptom onset, though treatment is still recommended for hospitalized or severely ill patients presenting beyond this window. 1, 2

Antiviral Therapy: Core Treatment Approach

First-Line Antiviral Agent

• Oseltamivir (Tamiflu) remains the antiviral drug of choice for managing illness caused by influenza A and B virus infections 1
• Standard adult dosing: 75 mg orally twice daily for 5 days 1, 2
• Dose adjustment required for renal impairment: reduce to 75 mg once daily if creatinine clearance <30 mL/min 1, 2
• Pediatric dosing is weight-based, ranging from 30-75 mg twice daily for children ≥12 months 1

Alternative Antiviral Options

• Inhaled zanamivir (Relenza) is an equally acceptable alternative for patients without chronic respiratory disease 1

  • Dosing: 10 mg (two 5-mg inhalations) twice daily for 5 days 1
  • Critical contraindication: Not recommended for patients with asthma or COPD due to risk of severe bronchospasm 1, 3
  • Licensed for treatment in children ≥7 years 1, 3

• Intravenous peramivir (Rapivab) for limited situations 1

  • Approved for children ≥2 years with acute uncomplicated influenza
  • Single dose: 12 mg/kg (maximum 600 mg) IV over 15-30 minutes 1
  • Efficacy in hospitalized patients with severe influenza has not been established 1

• Baloxavir for patients ≥12 years 1

  • Single oral dose: 40 mg for patients 40-80 kg; 80 mg for patients ≥80 kg 1

Timing of Antiviral Initiation: Critical Decision Points

Early Treatment (Within 48 Hours)

• Maximum benefit occurs when treatment starts within 24 hours of symptom onset 2, 4
• Reduces illness duration by approximately 1-1.5 days in otherwise healthy adults 1, 4
• Decreases risk of complications including pneumonia, hospitalization, and death 2, 5

Late Treatment (Beyond 48 Hours)

• Still recommended for hospitalized patients regardless of symptom duration 1, 2
• Still recommended for severely ill patients, particularly if immunocompromised 1, 2
• Evidence for benefit is limited but treatment should not be withheld in high-risk situations 1

Patient Selection for Antiviral Treatment

Mandatory Treatment Groups (Treat Regardless of Timing)

• All hospitalized patients with confirmed or suspected influenza 1, 2
• Patients with severe, complicated, or progressive illness 1, 2
• High-risk patients with chronic medical conditions (cardiac, pulmonary, renal, hepatic, neurologic, hematologic, metabolic disorders including diabetes) 2
• Immunocompromised patients 1, 2
• Children <2 years and adults ≥65 years 2
• Pregnant women and postpartum women within 2 weeks of delivery 2

Discretionary Treatment (Consider if Within 48 Hours)

• Previously healthy outpatients with uncomplicated influenza may be treated if presenting within 48 hours 1, 2
• Treatment can shorten symptom duration by approximately 1 day 1, 4
• Consider local influenza activity levels when making empiric treatment decisions 1

Patients Who May Not Require Treatment

• Previously healthy patients already beginning to recover 1
• Patients with uncomplicated febrile illness presenting beyond 48 hours who are not high-risk 1

Antibiotic Therapy: When to Add Bacterial Coverage

Uncomplicated Influenza Without Pneumonia

• Previously healthy adults with acute bronchitis do not routinely require antibiotics 1
• Consider antibiotics if worsening symptoms develop (recrudescent fever, increasing dyspnea) 1
• High-risk patients should receive antibiotics if lower respiratory features present 1

Non-Severe Influenza-Related Pneumonia

• Oral co-amoxiclav or tetracycline is preferred 1
• Alternative: macrolide (clarithromycin/erythromycin) or respiratory fluoroquinolone (levofloxacin, moxifloxacin) 1
• Parenteral options if oral contraindicated: IV co-amoxiclav or 2nd/3rd generation cephalosporin (cefuroxime, cefotaxime) 1
• Antibiotics must be administered within 4 hours of admission 1
• Duration: 7 days for uncomplicated pneumonia 1

Severe Influenza-Related Pneumonia

• Immediate parenteral combination therapy required 1
• Preferred regimen: IV broad-spectrum beta-lactam (co-amoxiclav or cefuroxime/cefotaxime) PLUS macrolide (clarithromycin/erythromycin) 1
• Alternative: respiratory fluoroquinolone plus broad-spectrum beta-lactam or macrolide 1
• Target pathogens: Streptococcus pneumoniae, Staphylococcus aureus (including MRSA), Streptococcus pyogenes 1
• Duration: 10 days for severe pneumonia; extend to 14-21 days if S. aureus or gram-negative bacteria suspected 1

Supportive Care

Symptomatic Management

• Oral antipyretics (acetaminophen or NSAIDs) with adequate oral hydration for uncomplicated influenza 6
• Use antipyretics only while symptoms persist 6

Hospitalized Patients

• IV fluids only when clinically indicated for volume depletion 6
• Oxygen therapy with monitoring for hypoxic patients 6

Monitoring and Red Flags

Warning Signs Requiring Immediate Medical Attention

• Shortness of breath or difficulty breathing 6
• Bloody sputum 6
• Drowsiness, disorientation, or confusion 6
• Fever persisting 4-5 days without improvement 6
• Initial improvement followed by recurrence of high fever 6

Hospitalization Criteria

• Temperature >37.8°C with unstable vital signs 6
• Heart rate >100/min 6
• Respiratory rate >24/min 6
• Systolic blood pressure <90 mmHg 6
• Oxygen saturation <90% 6

Chemoprophylaxis

Post-Exposure Prophylaxis

• Oseltamivir 75 mg once daily for 10 days for household contacts within 48 hours of exposure 1, 2
• Zanamivir 10 mg (two inhalations) once daily for 10 days as alternative 1
• Prophylaxis is not a substitute for vaccination 1, 2
• Prioritize for high-risk individuals and close contacts of vulnerable patients 1

Duration and Limitations

• Pre-exposure prophylaxis duration depends on community influenza activity 1
• Regimens up to 42 days for oseltamivir have been well-tolerated 1
• Limited role during widespread community activity due to supply concerns and resistance risk 1

Antiviral Resistance Considerations

• Almost all circulating influenza viruses since 2009 have been susceptible to oseltamivir 1
• Clinicians should monitor CDC weekly surveillance updates on antiviral susceptibility patterns 1
• If oseltamivir-resistant strains circulate, zanamivir remains effective 1
• Resistance can emerge during treatment but resistant variants typically have reduced fitness 5

Common Pitfalls to Avoid

• Do not withhold antiviral treatment from hospitalized patients presenting beyond 48 hours - they still benefit 1, 2
• Do not prescribe zanamivir to patients with asthma or COPD - risk of fatal bronchospasm 1, 3
• Do not delay antibiotics in severe pneumonia - must give within 4 hours of admission 1
• Do not use antibiotics for uncomplicated influenza in healthy patients - promotes resistance without benefit 1
• Do not rely on antiviral prophylaxis as primary prevention - vaccination remains essential 1, 2