What is the best approach to treating influenza (flu) patients?

Best Approach to Flu Patients

Start oseltamivir 75 mg orally twice daily for 5 days immediately if the patient presents within 48 hours of symptom onset with fever >38°C and acute influenza-like illness. 1, 2

Antiviral Treatment: The Foundation

Initiate oseltamivir as soon as possible—ideally within 24 hours of symptom onset—as earlier treatment provides maximum benefit. 3 The three criteria for outpatient antiviral treatment are: acute influenza-like illness, fever >38°C, and symptomatic for ≤48 hours. 1 However, hospitalized or severely ill patients should receive oseltamivir even if presenting beyond 48 hours, particularly if immunocompromised. 1, 4

Dosing and Special Populations

• Standard adult dose: oseltamivir 75 mg orally every 12 hours for 5 days 1, 2
• Reduce dose to 75 mg once daily if creatinine clearance <30 mL/min 5, 4, 2
• Elderly and immunocompromised patients may not mount adequate febrile response but remain eligible for treatment despite lack of documented fever 1
• Zanamivir (inhaled) is an alternative for patients unable to take oseltamivir 1, 6
• Do not delay treatment while awaiting laboratory confirmation—clinical diagnosis is sufficient 4, 3

Antibiotic Management: Stratified by Severity

Uncomplicated Influenza (No Pneumonia)

Previously healthy adults with acute bronchitis complicating influenza do NOT routinely require antibiotics. 5, 1 This is a critical pitfall to avoid—resist pressure to prescribe antibiotics for uncomplicated cases. 7

Consider antibiotics only if:

• Worsening symptoms develop (recrudescent fever or increasing dyspnea) 5, 1
• Patient is high-risk with lower respiratory tract features 5, 1

Non-Severe Influenza-Related Pneumonia

First-line oral therapy: co-amoxiclav or tetracycline (doxycycline) 5, 1, 7

Alternative options include macrolides (clarithromycin) or respiratory fluoroquinolones active against S. pneumoniae and S. aureus 5

Duration: 7 days for non-severe, uncomplicated pneumonia 1, 4

Severe Influenza-Related Pneumonia

Immediate IV combination therapy (within 4 hours of admission): 1, 4

• IV co-amoxiclav OR 2nd/3rd generation cephalosporin (cefuroxime, cefotaxime)
• PLUS a macrolide (clarithromycin or erythromycin) 5, 1, 4

Critical caveat: Never forget to cover S. aureus when treating influenza-related pneumonia—this is a particularly lethal combination. 4

Duration: 10 days for severe, microbiologically undefined pneumonia; 14-21 days if S. aureus or Gram-negative bacteria confirmed or strongly suspected 1, 4

Route Switching Strategy

Switch from IV to oral antibiotics when: 1, 4

• Clinical improvement occurs
• Temperature normal for 24 hours
• Oral route is feasible

Monitoring and Red Flags

In-Hospital Monitoring

Track vital signs at least twice daily (more frequently if severe): 5

• Temperature, respiratory rate, pulse, blood pressure
• Mental status, oxygen saturation, inspired oxygen concentration
• Use an Early Warning Score system for convenience 5, 4

Red Flags Requiring Immediate Re-evaluation

Watch for signs of bacterial superinfection or deterioration: 1, 4

• Shortness of breath at rest or painful breathing 1
• Coughing up bloody sputum 1
• Recrudescent fever (fever returning after initial improvement) 1, 4
• Increasing dyspnea 5, 1
• Altered mental status 5, 1
• Inability to maintain oral intake 5, 1
• Failure to improve after 3-5 days of antiviral treatment 4

Clinical deterioration after initial improvement is the classic pattern of bacterial superinfection—act immediately with empiric antibiotics. 4

Supportive Care

• Antipyretics for fever control (avoid aspirin in children <16 years due to Reye's syndrome risk) 1
• Adequate hydration 1, 8
• Oxygen therapy as needed (guided by arterial blood gases in COPD patients) 5
• Assess for cardiac complications and volume depletion 5
• Nutritional support in severe or prolonged illness 5

Discharge Criteria

Patients should have fewer than two of these unstable factors before discharge: 5, 4

• Temperature >37.8°C
• Heart rate >100/min
• Respiratory rate >24/min
• Systolic blood pressure <90 mmHg
• Oxygen saturation <90%
• Inability to maintain oral intake
• Abnormal mental status

Review patients 24 hours prior to discharge and arrange follow-up for those with significant complications or worsening of underlying disease. 5

Common Pitfalls to Avoid

• Never withhold oseltamivir while awaiting lab confirmation 4
• Never prescribe antibiotics for uncomplicated influenza without evidence of bacterial infection 1, 7
• Never delay empiric antibiotics if bacterial superinfection is suspected 4
• Never miss the 48-hour window for outpatient antiviral treatment—but remember hospitalized/severe patients benefit even beyond 48 hours 1, 4
• Never use azithromycin monotherapy for influenza-related pneumonia—it is inadequate 1