Management of Influenza A
For patients with suspected or confirmed influenza A, initiate oseltamivir 75 mg orally twice daily for 5 days immediately if the patient is hospitalized, has severe/progressive illness, or belongs to any high-risk group—regardless of symptom duration. 1, 2
Who Should Receive Antiviral Treatment
Immediate Treatment Required (Start Regardless of Time Since Symptom Onset)
- All hospitalized patients with suspected or confirmed influenza 3, 1, 2
- Patients with severe, complicated, or progressive illness (worsening dyspnea, hypoxemia, altered mental status) 1, 2
- High-risk patients, including: 3, 2
- Children younger than 2 years (highest risk in infants <6 months)
- Adults ≥65 years
- Pregnant women and postpartum women (within 2 weeks after delivery)
- Immunocompromised persons (HIV, medications, transplant recipients)
- Chronic medical conditions: pulmonary disease (including asthma), cardiovascular disease (except hypertension alone), renal disease, hepatic disease, diabetes, neurologic/neurodevelopmental conditions
- Morbidly obese (BMI ≥40)
- Residents of nursing homes or chronic care facilities
- American Indians/Alaska Natives
Consider Treatment for Lower-Risk Patients
- Previously healthy outpatients may benefit if treatment can start within 48 hours of symptom onset 1, 2, 4
- The 48-hour window applies primarily to otherwise healthy adults—hospitalized and high-risk patients benefit even when started >48 hours after symptom onset 1, 2
Antiviral Medication Options
First-Line Treatment
- Oseltamivir 75 mg orally twice daily for 5 days (adults with normal renal function) 1, 2, 4
- FDA-approved for treatment in patients ≥2 weeks of age who have been symptomatic for no more than 48 hours 4
- Use standard FDA-approved doses rather than higher doses for most patients 1
Alternative Agents
- Zanamivir (inhaled) for patients unable to take oseltamivir 5, 6
- FDA-approved for treatment in patients ≥7 years
- Contraindicated in patients with underlying airways disease (asthma, COPD) due to risk of serious bronchospasm 6
- Intravenous peramivir is available but not routinely recommended over oral oseltamivir 1
Special Populations
- Immunocompromised patients or those with severe lower respiratory tract disease may require longer duration of antiviral treatment 1
- Elderly patients (≥65 years) may not mount adequate febrile response but still require treatment based on clinical presentation 5, 2
When to Add Antibiotics
Do NOT Routinely Prescribe Antibiotics
- Uncomplicated influenza is a viral illness—antibiotics are not indicated unless bacterial coinfection is present 5, 2
- Previously healthy adults with acute bronchitis complicating influenza do not require antibiotics unless they develop worsening symptoms 5
Add Antibiotics Immediately If:
- Worsening symptoms after initial improvement (suggests secondary bacterial pneumonia) 1, 5, 2
- New or worsening dyspnea or shortness of breath 2
- Productive cough with purulent sputum 2
- Focal chest findings on examination 2
- Radiographic evidence of pneumonia 2
- Failure to improve after 3-5 days of antiviral treatment 1
Antibiotic Regimens for Influenza-Related Pneumonia
Non-Severe Pneumonia (Outpatient or Mild Hospitalized):
- First-line: Co-amoxiclav (amoxicillin-clavulanate) orally 1, 5, 2
- Alternatives: Doxycycline or respiratory fluoroquinolone 5, 2
- Duration: 7 days for uncomplicated pneumonia 5
Severe Pneumonia (Requiring Hospitalization):
- Immediate IV combination therapy within 4 hours of admission: 1, 5
- Co-amoxiclav OR 2nd/3rd generation cephalosporin (cefuroxime, cefotaxime)
- PLUS macrolide (clarithromycin or azithromycin)
- Switch from IV to oral when: clinical improvement occurs, temperature normal for 24 hours, and oral route feasible 1, 5
- Duration: 10 days for severe, microbiologically undefined pneumonia; 14-21 days if S. aureus or Gram-negative bacteria confirmed 5
Diagnostic Testing
When to Test
- RT-PCR or other molecular assays are preferred for diagnosing influenza in hospitalized patients due to superior sensitivity 1
- Rapid influenza diagnostic tests (RIDTs) should not be used in hospitalized patients except when molecular assays are unavailable, and negative results should be confirmed with RT-PCR 1
- For most outpatients, diagnosis should be made clinically, and the decision to begin antiviral therapy should not be delayed for laboratory confirmation 7, 8
Clinical Diagnosis
- Cough and fever together have a positive predictive value of 79% when influenza is circulating in the community 9
- Typical presentation: abrupt onset of fever, cough, myalgia, headache, severe malaise, sore throat, and rhinitis 3, 7
Severity Assessment and Hospital Admission
Use CURB-65 Score for Pneumonia Severity
- Score 0-1: Likely suitable for home treatment 3
- Score 2: Consider short inpatient stay or hospital-supervised outpatient treatment 3
- Score 3 or more: Manage in hospital as severe pneumonia 3
- New bilateral lung shadowing on chest x-ray consistent with primary viral pneumonia should be taken as a feature of severe pneumonia regardless of CURB-65 score 3
Indications for ICU Transfer
- Persisting hypoxia with PaO2 <8 kPa despite maximal oxygen 3
- Progressive hypercapnia 3
- Severe acidosis (pH <7.26) 3
- Septic shock 3
Supportive Care
- Antipyretics: Acetaminophen or ibuprofen for fever control 5, 2
- Adequate oral fluids or IV fluids if unable to maintain oral intake 2
- Supplemental oxygen to maintain SpO2 >92% 2
What NOT to Do
- Avoid corticosteroid adjunctive therapy for treatment of influenza unless clinically indicated for other reasons (e.g., COPD exacerbation, septic shock) 1
- Do not routinely administer immunoglobulin preparations for treatment of seasonal influenza 1
Red Flags Requiring Re-evaluation
- Shortness of breath at rest 5
- Painful or difficult breathing 5
- Coughing up bloody sputum 5
- Recrudescent fever (fever returning after initial improvement) 5
- Increasing dyspnea 5
- Altered mental status 5
- Inability to maintain oral intake 5
Monitoring for Antiviral Resistance
- Monitor for resistance in high-risk situations: 1
- Patients who develop influenza while on or immediately after neuraminidase inhibitor chemoprophylaxis
- Immunocompromised patients with persistent viral replication despite treatment
- Patients with severe influenza who don't improve with treatment