Treatment of Suspected Influenza
Start antiviral treatment immediately with oseltamivir for any hospitalized patient, any patient with severe or progressive illness, and all high-risk patients with suspected influenza—do not wait for test results or the 48-hour window. 1, 2, 3
Who Requires Immediate Antiviral Treatment
Mandatory Treatment Groups (Start Immediately, Regardless of Symptom Duration)
- Any hospitalized child or adult with suspected or confirmed influenza 1, 3
- Any patient with severe, complicated, or progressive illness attributable to influenza, whether inpatient or outpatient 1
- All high-risk patients with suspected influenza of any severity 1, 2, 3:
- Children younger than 2 years (highest risk under 6 months) 1, 3
- Adults ≥65 years 1, 2, 3
- Pregnant women and postpartum women (within 2 weeks after delivery) 1, 3
- Immunocompromised patients 1, 3
- Patients with chronic medical conditions: asthma, chronic pulmonary disease, cardiovascular disease (except hypertension alone), diabetes, renal disease, hepatic disease, hematologic disorders including sickle cell disease, neurologic/neurodevelopmental conditions, metabolic disorders 1, 3
- Morbidly obese patients (BMI ≥40) 1
- American Indian/Alaska Native persons 1
- Residents of nursing homes and chronic care facilities 1
Optional Treatment Groups
- Previously healthy outpatients with uncomplicated influenza may be considered for treatment if initiated within 48 hours of symptom onset, though benefit is modest (reduces illness duration by approximately 24-36 hours) 1, 3
- Children with influenza whose household contacts are younger than 6 months or have high-risk conditions 1
First-Line Antiviral Medication and Dosing
Oseltamivir (Preferred Agent)
Adults and adolescents ≥13 years: 75 mg orally twice daily for 5 days 1, 4
Pediatric patients (weight-based dosing): 1, 4
- Infants 2 weeks to <1 year: 3 mg/kg twice daily for 5 days
- Children 1-12 years:
- ≤15 kg: 30 mg twice daily
- 15.1-23 kg: 45 mg twice daily
- 23.1-40 kg: 60 mg twice daily
40 kg: 75 mg twice daily
Duration: Standard treatment is 5 days; consider longer duration for immunocompromised patients or those with severe lower respiratory tract disease 3, 5
Renal dosing: Reduce dose by 50% if creatinine clearance <30 mL/min 4
Administration: May be taken with or without food, but tolerability is enhanced with food 4
Alternative Agents
- Zanamivir (inhaled): 10 mg (two 5-mg inhalations) twice daily for 5 days; acceptable alternative for patients without chronic respiratory disease 1
- Peramivir (IV): Approved for children ≥2 years with acute uncomplicated influenza who have been symptomatic ≤2 days and are not hospitalized 1
Critical Timing Considerations
- Initiate treatment as soon as influenza is suspected—do not delay for diagnostic test results 1, 2, 3
- Greatest benefit occurs when started within 48 hours of symptom onset, but even greater benefit when started within 24 hours 1, 2
- Treatment beyond 48 hours is still beneficial for hospitalized patients, those with severe disease, and high-risk patients 1
- Observational studies show that treatment initiated even <5 days after onset in severely ill patients reduces morbidity and mortality 1
Diagnostic Testing Approach
- RT-PCR or molecular assays are preferred for diagnosis due to superior sensitivity 2, 5
- Do not use rapid antigen tests to rule out influenza—they have low sensitivity, particularly for H1N1 strains; negative results should not guide treatment decisions 1, 5
- Treatment should never be delayed while awaiting test results in high-risk or severely ill patients 3, 5
- In hospitalized patients, multiplex RT-PCR targeting respiratory pathogens should be used, especially in immunocompromised patients 5
Managing Complications and Treatment Failure
When to Suspect Bacterial Coinfection
Empirically add antibiotics to antiviral therapy if: 2, 3, 5
- Severe initial presentation
- Clinical deterioration after initial improvement
- Failure to improve after 3-5 days of antiviral treatment
- Persistent or recrudescent fever
Antibiotic Selection for Influenza-Related Pneumonia
Non-severe pneumonia (outpatient): 2, 5
- Co-amoxiclav (amoxicillin-clavulanate) OR
- Doxycycline
Severe pneumonia (hospitalized): 3, 5
- IV co-amoxiclav OR
- 2nd/3rd generation cephalosporin PLUS macrolide
Duration: Typically 7 days; switch to oral when afebrile for 24 hours and clinically improving 3
Key pathogens: Streptococcus pneumoniae, Staphylococcus aureus (including MRSA), Streptococcus pyogenes 3
Common Pitfalls to Avoid
- Do not withhold treatment from high-risk patients presenting beyond 48 hours—they still benefit significantly 1
- Do not rely on rapid antigen tests to exclude influenza; their low sensitivity makes them unreliable for clinical decision-making 1, 5
- Do not use amantadine or rimantadine—high levels of resistance exist against these agents 1
- Do not routinely use corticosteroids for influenza treatment unless clinically indicated for other reasons 5
- Do not use immunoglobulin preparations routinely for seasonal influenza 5
- Do not prescribe antibiotics empirically for uncomplicated influenza without evidence of bacterial coinfection (30% of influenza patients inappropriately receive antibiotics) 6
Special Population Considerations
Immunocompromised Patients
- May benefit from treatment even without documented fever 3
- Higher risk of prolonged viral shedding and complications 3
- Consider extended treatment duration (up to 12 weeks for prophylaxis) 4
- Monitor for antiviral resistance, especially if developing influenza while on or immediately after prophylaxis 5
Pregnant and Postpartum Women
- Oseltamivir is safe and recommended 3
- Should receive treatment immediately as a high-risk group 1, 3
- Women in postpartum period who did not receive vaccination during pregnancy should receive influenza vaccine before hospital discharge 1