What are the guidelines for managing influenza (flu)?

Influenza Management Guidelines

Antiviral treatment with oseltamivir should be initiated within 48 hours of symptom onset in patients with influenza-like illness and fever >38°C. 1

Assessment and Diagnosis

Clinical Presentation

• Acute influenza-like illness (ILI) with fever (>38°C in adults, >38.5°C in children)
• Common symptoms: cough, sore throat, myalgia, headache, fatigue
• Many infants and children may have coughs and mild fevers due to other infections such as respiratory syncytial virus, especially during winter months 2

Risk Assessment

• Identify patients at high risk for complications:
  • Elderly (≥65 years)
  • Children <1 year
  • Patients with chronic conditions (pulmonary, cardiac, renal, metabolic disorders)
  • Immunocompromised individuals 2
  • Pregnant women

Severity Assessment

• For patients with suspected pneumonia, use CRB-65 score to determine management:
  • Confusion (Mental Test Score <8, or new disorientation)
  • Respiratory rate >30/min
  • Blood pressure (SBP <90 mmHg or DBP ≤60 mmHg)
  • Age >65 years
  • Score 0: Suitable for home treatment
  • Score 1-2: Consider hospital referral (especially with score 2)
  • Score 3-4: Urgent hospital referral 2
  • Bilateral chest signs of pneumonia: Consider hospital referral regardless of score

Treatment Approach

Antiviral Therapy

1. First-line treatment: Oseltamivir (Tamiflu)

   • Dosing for adults: 75 mg twice daily for 5 days 2, 1
   • Dosing for children ≥1 year:
     • ≤15 kg: 30 mg twice daily
     • 15-23 kg: 45 mg twice daily

     • 24 kg: 75 mg twice daily 2

   • Renal adjustment: Reduce dose to 75 mg once daily if creatinine clearance <30 ml/min 2, 1
   • Timing: Start within 48 hours of symptom onset for maximum benefit 2, 1

2. Special considerations:

   • Immunocompromised or elderly patients may benefit from treatment even without documented fever 1
   • Hospitalized patients with severe illness may benefit from antiviral treatment started >48 hours from disease onset 2
   • Most common side effect: nausea (10% of patients), which can be managed with mild anti-emetics 2

3. Expected benefits:

   • Reduction of illness duration by approximately 24 hours
   • Possible reduction in hospitalization
   • Reduction in subsequent antibiotic use 2

Antibiotic Therapy

• Not complicated by pneumonia:

  • Previously well adults: Antibiotics not routinely required
  • Patients with worsening symptoms (recrudescent fever or increasing dyspnea): Consider antibiotics
  • Patients with COPD or other severe pre-existing illnesses: Antibiotics recommended 2

• Complicated by pneumonia:

  • Oral therapy with co-amoxiclav or a tetracycline (e.g., doxycycline) is preferred
  • Alternative: Macrolide (e.g., clarithromycin) for those intolerant to first choices 2

Monitoring and Follow-up

Home Management

• Monitor for signs requiring re-consultation:
  • Shortness of breath at rest or with minimal activity
  • Painful or difficult breathing
  • Hemoptysis
  • Drowsiness, disorientation, or confusion
  • Fever for 4-5 days without improvement
  • Initial improvement followed by recurrent high fever
  • Lack of improvement after 2 days of antiviral therapy 2

Hospital Monitoring

• Monitor vital signs at least twice daily using Early Warning Score system 2, 1
• Reassess patients not progressing satisfactorily with clinical examination and repeat chest radiograph 2

Discharge Criteria

• Review patients 24 hours prior to discharge
• Consider continued hospitalization if two or more of the following are present:
  • Temperature >37.8°C
  • Heart rate >100/min
  • Respiratory rate >24/min
  • Systolic blood pressure <90 mmHg
  • Oxygen saturation <90% 2

Prevention

• Vaccination remains the cornerstone for influenza prophylaxis 2
• Antiviral drugs are not a substitute for influenza vaccination but can be used as adjuncts 3
• Oseltamivir may be used for post-exposure prophylaxis in high-risk individuals 4

Special Considerations

• Baloxavir is indicated for treatment of acute uncomplicated influenza in patients 5 years and older who have been symptomatic for no more than 48 hours 4
• Avoid administration of live attenuated influenza vaccine (LAIV) within 2 weeks or 48 hours after oseltamivir administration 5
• Patients with hereditary fructose intolerance should be informed that oseltamivir oral suspension contains sorbitol 5

Remember that antiviral therapy is most effective when initiated early, and vaccination remains the most effective preventive measure against influenza.