What is the recommended management for patients with influenza-like illness?

Management of Influenza-Like Illness

For patients with influenza-like illness presenting within 48 hours of symptom onset with fever >38°C, initiate oseltamivir 75 mg orally twice daily for 5 days; otherwise healthy adults without pneumonia do not require antibiotics unless they develop worsening symptoms. 1, 2

Antiviral Treatment Criteria

Initiate oseltamivir only if ALL three criteria are met: 1

• Acute influenza-like illness (fever, cough, myalgias, malaise) 1
• Fever >38°C (documented or reported) 1
• Symptomatic for ≤48 hours 1, 2

Standard dosing: Oseltamivir 75 mg orally every 12 hours for 5 days 1, 2

Dose adjustment: Reduce to 75 mg once daily if creatinine clearance <30 mL/min 1

Important Exceptions to the 48-Hour Rule

Consider antiviral treatment beyond 48 hours for: 1

• Hospitalized patients who are severely ill 1
• Immunocompromised patients (regardless of hospitalization status) 1
• Patients unable to mount adequate febrile response (very elderly, immunocompromised) who may lack documented fever 1

Note: Evidence for benefit beyond 48 hours in these populations is lacking, but potential benefit may outweigh minimal risk 1

Antibiotic Management: Stratified by Severity

Uncomplicated Influenza (No Pneumonia)

Do NOT routinely prescribe antibiotics for previously healthy adults with acute bronchitis complicating influenza in the absence of pneumonia 1

Consider antibiotics only if: 1

• Worsening symptoms develop (recrudescent fever or increasing dyspnea) 1
• Patient is at high risk of complications (elderly, chronic cardiac/respiratory disease, immunocompromised) AND has lower respiratory tract features 1

First-line oral antibiotics when indicated: 1

• Co-amoxiclav (preferred) 1
• Tetracycline (alternative) 1
• Macrolide (clarithromycin or erythromycin) for penicillin-intolerant patients 1

Non-Severe Influenza-Related Pneumonia

Most patients can be treated with oral antibiotics: 1

Preferred oral regimens: 1

• Co-amoxiclav (first choice) 1
• Tetracycline (alternative) 1

If oral therapy contraindicated, use parenteral: 1

• IV co-amoxiclav 1
• Second-generation cephalosporin (cefuroxime) 1
• Third-generation cephalosporin (cefotaxime) 1

Alternative for penicillin allergy: Macrolide or respiratory fluoroquinolone (levofloxacin or moxifloxacin) with activity against S. pneumoniae and S. aureus 1

Timing: Administer antibiotics within 4 hours of admission 1

Severe Influenza-Related Pneumonia

Treat immediately with parenteral antibiotics upon diagnosis: 1

Preferred combination regimen: 1

• IV broad-spectrum beta-lactamase stable antibiotic (co-amoxiclav OR second/third-generation cephalosporin) 1
• PLUS IV macrolide (clarithromycin or erythromycin) 1

Alternative regimen: 1

• Respiratory fluoroquinolone with enhanced pneumococcal activity 1
• PLUS broad-spectrum beta-lactamase stable antibiotic OR macrolide 1

Antibiotic Duration and Route Switching

Switch from IV to oral when: 1

• Clinical improvement occurs 1
• Temperature normal for 24 hours 1
• No contraindication to oral route 1

Duration of therapy: 1

• Non-severe, uncomplicated pneumonia: 7 days 1
• Severe, microbiologically undefined pneumonia: 10 days 1
• Confirmed/suspected S. aureus or Gram-negative pneumonia: 14-21 days 1

Management of Treatment Failure

For non-severe pneumonia not responding to combination therapy: 1

• Switch to fluoroquinolone with effective pneumococcal and staphylococcal coverage 1

For severe pneumonia not responding to combination therapy: 1

• Add antibiotics effective against MRSA 1

Supportive Care

All patients should receive: 1, 3

• Antipyretics for fever control 1
• Adequate hydration 1
• Avoid aspirin in children (risk of Reye's syndrome) 1, 3

For hospitalized patients, monitor: 1

• Cardiac complications 1
• Volume depletion and IV fluid needs 1
• Nutritional support in severe/prolonged illness 1

Critical Pitfalls to Avoid

Do not prescribe zanamivir to patients with asthma or COPD (risk of fatal bronchospasm; oseltamivir is the only safe neuraminidase inhibitor in these patients) 4

Watch for secondary bacterial pneumonia, which typically develops 4-5 days after initial influenza symptoms with new/worsening fever, increasing dyspnea, or purulent sputum 5, 3

Recognize that S. aureus (including MRSA) is a particularly important pathogen in influenza-related secondary bacterial pneumonia and has high mortality 6

Do not withhold antivirals from high-risk patients (pregnant women, immunocompromised, chronic cardiac/respiratory disease) even if presenting slightly beyond 48 hours, as they may still benefit significantly 4, 7

Standard streptococcal pharyngitis antibiotics (penicillin/amoxicillin) do NOT provide adequate coverage for influenza-related bacterial complications; use co-amoxiclav or broader agents when pneumonia is suspected 5