What is the recommended treatment for influenza infection presentation?

Treatment of Influenza Infection

Initiate oseltamivir 75 mg orally twice daily for 5 days immediately in all hospitalized patients, severely ill patients, or high-risk patients with suspected or confirmed influenza, regardless of symptom duration or vaccination status. 1, 2, 3

Who Should Receive Antiviral Treatment

Mandatory Treatment Groups (Start Immediately)

• All hospitalized patients with suspected or confirmed influenza, even if presenting >48 hours after symptom onset 4, 1, 2
• Patients with severe, progressive, or complicated illness at any age 4, 1
• All high-risk patients, including:
  • Children <2 years and adults ≥65 years 4, 1, 2
  • Pregnant and postpartum women 1, 2
  • Immunocompromised patients 1, 2
  • Chronic medical conditions (asthma, diabetes, cardiac/pulmonary disease, neurologic disorders, renal/hepatic disease) 4, 1, 2

Optional Treatment (Clinical Judgment)

• Previously healthy outpatients with uncomplicated influenza may be treated if presenting within 48 hours of symptom onset, though benefit is modest (reduces illness duration by approximately 24 hours) 4, 2, 5
• Treatment decisions should be informed by local influenza activity—empiric treatment when community prevalence is low results in unnecessary antiviral use 4

Antiviral Regimen

Standard Dosing

• Oseltamivir 75 mg orally twice daily for 5 days is the preferred treatment 1, 2, 3
• Treatment is most effective when started within 48 hours of symptom onset, but hospitalized and severely ill patients benefit even when started >48 hours after onset 4, 1, 6
• The greatest benefit occurs when treatment begins within 24 hours of symptom onset 5

Alternative Agents

• Zanamivir (inhaled) is an alternative for patients unable to take oseltamivir 1, 6
• Peramivir (single IV dose) can be used for uncomplicated influenza 1
• Baloxavir is another option with a different mechanism of action 7

Dose Adjustments

• Renal impairment: Reduce oseltamivir to 75 mg once daily if creatinine clearance <30 mL/min 1, 3
• Immunocompromised or severely ill patients may require treatment duration >5 days 1, 2
• Pediatric dosing: Weight-based dosing for children 2 weeks to 12 years (see FDA label for specific weights) 3

Antibiotic Management for Bacterial Complications

When NOT to Use Antibiotics

• Previously healthy adults with uncomplicated influenza or acute bronchitis do not require antibiotics 1, 6, 2

When to Add Antibiotics

Add antibiotics immediately if any of the following are present:

• Worsening symptoms after initial improvement 6, 2
• Radiographic evidence of pneumonia 1, 6
• High-risk patients with lower respiratory tract features 6, 2

Antibiotic Regimens for Influenza-Related Pneumonia

Non-severe pneumonia (oral therapy):

• First-line: Co-amoxiclav or tetracycline 1, 6, 2
• Alternatives: Macrolides or fluoroquinolones with pneumococcal and staphylococcal activity 1, 2
• Duration: 7 days for uncomplicated cases 1, 6

Severe pneumonia (parenteral therapy):

• IV co-amoxiclav or 2nd/3rd generation cephalosporin (cefuroxime, cefotaxime) PLUS macrolide (clarithromycin or erythromycin) 1, 6, 2
• Must be administered within 4 hours of admission 6
• Switch to oral when clinically improved, afebrile for 24 hours, and oral route feasible 1, 6
• Duration: 10 days for severe, microbiologically undefined pneumonia; 14-21 days for confirmed/suspected S. aureus or Gram-negative pneumonia 6

Critical Consideration

• Staphylococcus aureus (including MRSA) is a more frequent cause of secondary pneumonia during influenza epidemics than in typical community-acquired pneumonia—ensure antibiotic coverage addresses this pathogen 4, 1, 2

Critical Pitfalls to Avoid

• Never delay antiviral treatment while awaiting laboratory confirmation in hospitalized or high-risk patients—clinical diagnosis is sufficient 1, 2
• Never withhold oseltamivir from high-risk or hospitalized patients presenting >48 hours after symptom onset, as they still benefit significantly 4, 1, 2
• Never use zanamivir in patients with underlying respiratory disease (asthma, COPD) due to risk of severe bronchospasm 1, 2
• Never use aspirin in children <16 years with influenza due to Reye syndrome risk 6, 2
• Never rely on negative rapid antigen tests to rule out influenza—they have low sensitivity 2
• Never use antibiotics systematically in uncomplicated influenza without evidence of bacterial infection 1, 2
• Remember oseltamivir may be less effective against influenza B than influenza A 4, 1

Supportive Care

• Antipyretics for fever control (avoid aspirin in children) 6, 2
• Adequate hydration 6
• Rest 6
• Oseltamivir may be taken with or without food, though tolerability is enhanced with food 3

Red Flags Requiring Re-evaluation

Patients should be instructed to return if they develop:

• Shortness of breath at rest or painful/difficult breathing 6
• Coughing up bloody sputum 6
• Recrudescent fever (fever returning after initial improvement) 6
• Altered mental status 6
• Inability to maintain oral intake 6