What is the recommended treatment for patients suspected of having Influenza A or B, especially those in high-risk groups such as the elderly, young children, or individuals with compromised immune systems?

Treatment of Influenza A and B

Start antiviral treatment immediately with oseltamivir for all hospitalized patients, severely ill patients, and high-risk individuals (children <2 years, adults ≥65 years, pregnant/postpartum women, immunocompromised patients, and those with chronic conditions) regardless of symptom duration or vaccination status. 1, 2

Who Requires Immediate Antiviral Treatment

Mandatory Treatment Groups

• Any hospitalized patient with suspected or confirmed influenza, regardless of how long symptoms have been present 1, 2
• Severely ill or progressively worsening patients at any age, including those with pneumonia, respiratory failure, or other complications 1, 2, 3
• All high-risk patients presenting with influenza-like illness, even in outpatient settings 1, 2

High-Risk Groups Requiring Treatment

• Children aged <2 years (highest risk in infants <6 months) 1, 4
• Adults aged ≥65 years 1, 2
• Pregnant women and postpartum women (within 2 weeks after delivery) 1, 2
• Immunocompromised patients, including those on chronic corticosteroids or with HIV 1, 2
• Patients with chronic conditions: pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, hematological, metabolic (including diabetes), or neurologic disorders 1, 2
• Morbidly obese patients (BMI ≥40) 1
• Residents of nursing homes and chronic-care facilities 1
• American Indians/Alaska Natives 1
• Children <19 years receiving long-term aspirin therapy 1

Timing of Treatment Initiation

Do not delay treatment while awaiting laboratory confirmation in high-risk or hospitalized patients. 1, 2, 4 Treatment should begin empirically based on clinical suspicion during influenza season. 1, 2

• Optimal benefit: Treatment started within 48 hours of symptom onset, with greatest benefit when initiated within 12-36 hours 1, 4
• Beyond 48 hours: Still initiate treatment in hospitalized, severely ill, or high-risk patients as mortality benefit may persist 1, 2, 3
• Complete the full treatment course even if initial testing is negative, unless an alternative diagnosis is established 1

Recommended Antiviral Regimens

First-Line Treatment: Oseltamivir

Adults and adolescents ≥13 years:

• 75 mg orally twice daily for 5 days 2, 4, 3
• Reduces illness duration by approximately 24 hours and may decrease hospitalization rates 4

Pediatric dosing (≥12 months): 4

• ≤15 kg: 30 mg twice daily
• 15-23 kg: 45 mg twice daily
• 24-40 kg: 60 mg twice daily

• 40 kg: 75 mg twice daily

Infants <12 months: 4

• 9-11 months: 3.5 mg/kg per dose twice daily
• 0-8 months: 3 mg/kg per dose twice daily

Preterm infants: 4

• <38 weeks postmenstrual age: 1.0 mg/kg twice daily
• 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily

• 40 weeks postmenstrual age: 3.0 mg/kg twice daily

Renal dose adjustment: Reduce dose to 75 mg once daily if creatinine clearance <30 mL/min 1, 2, 4

Alternative Antiviral Agents

Zanamivir (inhaled):

• 10 mg (two 5-mg inhalations) twice daily for 5 days 4, 5
• Approved for ages ≥7 years for treatment, ≥5 years for prophylaxis 4, 5
• Contraindicated in patients with underlying respiratory disease (asthma, COPD) due to risk of severe bronchospasm 2, 5

Peramivir (IV):

• Consider for severely ill patients with concerns about oral absorption 4
• Single intravenous dose option available 2

Amantadine and rimantadine:

• Not recommended due to high resistance rates among current influenza A strains 4, 3

Duration of Treatment

• Standard duration: 5 days for most patients 2, 4, 3
• Extended duration: Consider longer treatment for immunocompromised patients, critically ill patients, or those with persistent fever after 6 days 2, 4

Managing Bacterial Coinfection

When to add antibiotics: 2, 4, 3

• Initial presentation with severe disease
• Clinical deterioration after initial improvement
• Failure to improve after 3-5 days of antiviral treatment
• Worsening symptoms suggesting bacterial pneumonia

Antibiotic selection for influenza-related pneumonia:

Non-severe pneumonia (outpatient): 2, 4

• First-line: Co-amoxiclav or tetracycline orally
• Alternatives: Macrolides or fluoroquinolones

Severe pneumonia (hospitalized): 2, 4

• IV combination therapy: Broad-spectrum β-lactamase stable antibiotic (e.g., co-amoxiclav) plus macrolide
• Initiate within 4 hours of admission
• Consider Staphylococcus aureus coverage during influenza epidemics, as it causes secondary pneumonia more frequently than in typical community-acquired pneumonia 2

Pediatric antibiotic dosing: 1

• Co-amoxiclav: 30 mg/kg three times daily IV
• Clarithromycin: 5-7 mg/kg twice daily IV
• Cefuroxime: 20-30 mg/kg three times daily IV

Chemoprophylaxis Recommendations

Post-exposure prophylaxis indications: 1

• High-risk children for whom influenza vaccine is contraindicated
• High-risk children during the 2 weeks after vaccination (before optimal immunity develops)
• Unvaccinated family members or healthcare personnel with close exposure to unvaccinated high-risk children or infants <24 months
• Control of outbreaks in institutional settings with high-risk residents
• High-risk immunocompromised patients who may not respond adequately to vaccination

Prophylaxis dosing:

• Oseltamivir 75 mg once daily for 10 days (post-exposure) or up to 6 weeks (seasonal prophylaxis during community outbreaks) 4
• Initiate within 48 hours of exposure 4

Critical Pitfalls to Avoid

• Never delay antiviral treatment while awaiting virological confirmation in hospitalized or high-risk patients 2, 3
• Do not use antibiotics systematically in uncomplicated influenza without evidence of bacterial infection 2, 4
• Avoid zanamivir in patients with asthma or COPD due to severe bronchospasm risk 2, 5
• Do not use corticosteroids as adjunctive therapy for seasonal influenza 3
• Remember that Staphylococcus aureus is a more frequent cause of secondary pneumonia during influenza epidemics 2
• Consider that oseltamivir may be less effective against influenza B than influenza A 2
• Take oseltamivir with food to reduce gastrointestinal side effects (nausea/vomiting occur in 10-15% of patients) 4
• Do not use amantadine or rimantadine due to widespread resistance 4, 3

Vaccination Considerations

• Antiviral treatment is not a substitute for annual influenza vaccination 1
• Pregnant women should receive inactivated influenza vaccine (IIV) at any time during pregnancy 1
• Postpartum women who did not receive vaccination during pregnancy should receive vaccine before hospital discharge 1
• Children with egg allergy can receive influenza vaccine without additional precautions 1
• Healthcare personnel vaccination is crucial for preventing healthcare-associated influenza infections 1