What are the guidelines for managing Influenza A?

Management Guidelines for Influenza A

Neuraminidase inhibitors (oseltamivir or zanamivir) should be started as soon as possible within 48 hours of symptom onset in patients with confirmed or suspected influenza A, particularly for those at high risk of complications. 1

Diagnosis

• Diagnosis of influenza A should be made clinically in most outpatient settings, based on acute onset of fever, cough, myalgias, and malaise during influenza season 2
• Laboratory testing is recommended for hospitalized patients and those where confirmation would change management decisions 1
• Preferred diagnostic tests include rapid molecular assays (nucleic acid amplification tests) over rapid influenza diagnostic tests (RIDTs) for improved detection 1
• Collect nasopharyngeal specimens (optimal) or mid-turbinate nasal swabs rather than throat swabs for better detection 1
• For hospitalized patients with respiratory failure on mechanical ventilation, collect endotracheal aspirate or bronchoalveolar lavage fluid specimens 1

Antiviral Treatment

Who to Treat

• Initiate antiviral treatment as soon as possible for the following patients regardless of vaccination status 1:
  • Hospitalized patients with influenza, regardless of illness duration
  • Outpatients with severe or progressive illness
  • High-risk patients including those with chronic medical conditions and immunocompromised patients
  • Children younger than 2 years and adults ≥65 years
  • Pregnant women

Medication Selection

• Oseltamivir (Tamiflu) is the preferred first-line treatment 1, 3:

  • Adults and children >24kg: 75 mg twice daily for 5 days
  • Children 15-23 kg: 45 mg twice daily for 5 days
  • Children ≤15 kg: 30 mg twice daily for 5 days
  • Reduce dose by 50% if creatinine clearance is less than 30 ml/minute

• Zanamivir (Relenza) is an alternative for patients ≥7 years old: 10 mg (two 5-mg inhalations) twice daily for 5 days 4

  • Not recommended for patients with underlying airways disease due to risk of bronchospasm

Expected Benefits

• Reduction of illness duration by approximately 24 hours 1, 5
• Possible reduction in hospitalization rates 1
• Reduction in subsequent antibiotic use 1
• Reduction in lower respiratory tract complications with oseltamivir 150 mg daily 5

Management of Uncomplicated Influenza

• Provide symptomatic treatment including rest, hydration, and antipyretics 1
• Patients should start to improve within 48 hours of starting antiviral therapy; failure to improve is an indication to re-consult 1
• Monitor for warning signs that should prompt re-consultation 1:
  • Shortness of breath at rest or with minimal activity
  • Painful or difficult breathing
  • Coughing up bloody sputum
  • Drowsiness, disorientation or confusion
  • Persistent fever for 4-5 days without improvement
  • Initial improvement followed by recrudescent fever and worsening symptoms

Management of Influenza Complications

Pneumonia

• Assess severity using CRB-65 score to guide management 1:

  • Score 0: Suitable for home treatment
  • Score 1-2: Consider hospital referral (especially with score 2)
  • Score 3-4: Urgent hospital referral
  • Any score with bilateral chest signs of pneumonia: Consider hospital referral

• For non-severe influenza-related pneumonia, oral therapy with co-amoxiclav or a tetracycline (e.g., doxycycline) is preferred 1

• For patients unable to take oral medications, parenteral options include IV co-amoxiclav or a second/third generation cephalosporin 1

Antibiotic Use

• Antibiotics are not routinely required for previously well patients with uncomplicated influenza or simple bronchitis 1
• Consider antibiotics for patients who develop worsening symptoms (recrudescent fever or increasing dyspnoea) 1
• Strongly consider antibiotics for patients with COPD and/or other severe pre-existing illnesses 1
• Recommended antibiotics include a tetracycline (e.g., doxycycline) or co-amoxiclav; a macrolide (e.g., clarithromycin) is an alternative for those intolerant to first-line options 1

Special Populations

Hospitalized Patients

• Use RT-PCR or other molecular assays over other influenza tests for improved detection 1
• Consider multiplex RT-PCR assays targeting a panel of respiratory pathogens in immunocompromised patients 1
• Monitor temperature, respiratory rate, pulse, blood pressure, mental status, and oxygen saturation at least twice daily 1
• Reassess patients not progressing satisfactorily with a full clinical evaluation and repeat chest radiograph 1

Outbreak Management

• During facility outbreaks 1:
  • Perform rapid influenza virus testing on nasopharyngeal specimens from patients with recent symptom onset
  • Administer current influenza vaccine to unvaccinated patients and healthcare personnel
  • Consider antiviral prophylaxis for all patients without influenza in the involved unit
  • Administer appropriate antiviral treatment to patients with influenza within 48 hours of illness onset

Prevention

• Annual influenza vaccination remains the primary preventive measure 1, 2
• Consider antiviral prophylaxis with oseltamivir (75 mg once daily) for unvaccinated high-risk individuals during local influenza activity 6
• For post-exposure prophylaxis in household contacts, oseltamivir has shown protective efficacy of 58.5-89% when started within 48 hours of index case symptom onset 5