Influenza

Treat suspected or confirmed influenza as soon as possible, irrespective of illness duration, in any hospitalized patient; any outpatient with severe, complicated, or progressive illness; and any outpatient at higher risk for influenza complications. Prior-season vaccination does not exclude influenza and should not delay treatment.PubMed+2PubMedClinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal InfluenzaaPubMedInfluenza - CDC Yellow Book, 2026 edition - NCBI BookshelfCDCCoCA Slides for December 11, 2025

Use immediate clinical escalation for pneumonia, sepsis, hypoxemic respiratory illness, or exacerbation of an underlying chronic disease associated with suspected influenza. Hospitalized patients with severe respiratory disease should also be assessed for possible influenza and SARS-CoV-2 coinfection, using multiplex testing when the result will guide isolation or pathogen-directed management.WHO+1WHOWHO EMRO - COVID-19 and influenzaPubMedInfluenza - CDC Yellow Book, 2026 edition - NCBI Bookshelf

For a previously healthy outpatient without high-risk conditions, treatment is discretionary rather than mandatory. Consider empiric antiviral therapy only when it can begin within 48 hours of symptom onset, including after telemedicine assessment when the clinical syndrome and local circulation make influenza likely.PubMed+2PubMedClinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal InfluenzaaPubMedInfluenza in Children and Adolescents: Epidemiology, Management, and PreventionCDCCoCA Slides for December 11, 2025

Most outpatients with uncomplicated illness compatible with influenza during active community circulation do not require testing solely to make an empiric treatment decision. Test when the result will determine antiviral use in a nonpriority patient, trigger additional evaluation, modify infection-control actions, or guide chemoprophylaxis for contacts.PubMed+1PubMedInfluenza in Children and Adolescents: Epidemiology, Management, and PreventionPubMedInfluenza - CDC Yellow Book, 2026 edition - NCBI Bookshelf

Interpret rapid influenza diagnostic tests in the context of local prevalence. RIDTs have high specificity, generally greater than 90%, but low-to-moderate sensitivity of 20%-70% compared with more sensitive methods. During high influenza activity, a negative RIDT should not be used to withhold treatment from a patient who otherwise meets a treatment indication.CDCCDCAntiviral Agents for the Treatment and Chemoprophylaxis of Influenza

If definitive confirmation is necessary after a negative RIDT, use RT-PCR or another molecular assay rather than repeating antigen testing. A positive RIDT is more reliable when influenza activity is high; during low activity, its positive predictive value falls and a positive result requires more cautious interpretation.CDCCDCAntiviral Agents for the Treatment and Chemoprophylaxis of Influenza

Use oral or enteric oseltamivir as the preferred treatment for patients who are hospitalized, have severe or complicated influenza, or are at increased risk for complications and can tolerate enteral therapy. CDC identifies oseltamivir as the recommended treatment across all ages; 2025-2026 CDC materials specify twice-daily administration for 5 days for treatment.PubMed+1PubMedInfluenza - CDC Yellow Book, 2026 edition - NCBI BookshelfCDCCoCA Slides for December 11, 2025

For uncomplicated influenza, FDA-approved options include oral oseltamivir, inhaled zanamivir, intravenous peramivir, and oral single-dose baloxavir, with age restrictions that determine selection. Oseltamivir is FDA-approved for early uncomplicated treatment from age 2 weeks; peramivir from age 6 months; zanamivir from age 7 years; and baloxavir from age 5 years, with baloxavir approval in ages 5 to under 12 years limited to otherwise healthy children and use in all persons aged 12 years or older.CDC+1CDCAbout Influenza Antiviral Medications | Influenza (Flu) | CDCCDCCoCA Slides for December 11, 2025

Avoid inhaled zanamivir in patients with chronic respiratory disease because bronchospasm may occur. Consider intravenous peramivir for a patient unable to tolerate or absorb oral antiviral therapy, recognizing that it is administered as a single infusion and requires dose reduction when baseline creatinine clearance is below 50 mL/min.JAMA+3JAMAComparison of Antiviral Agents for Seasonal Influenza ...PubMedInfluenza - CDC Yellow Book, 2026 edition - NCBI BookshelfCDCCoCA Slides for December 11, 2025CDCInfluenza Antiviral Medications: Summary for Clinicians | Influenza (Flu) | CDC

Counsel according to agent-specific adverse effects: oseltamivir commonly causes nausea and vomiting, zanamivir can cause bronchospasm, and peramivir can cause diarrhea. These risks matter most when choosing an alternative agent for a patient with active vomiting, obstructive lung disease, or difficulty maintaining enteral intake.JAMAJAMAComparison of Antiviral Agents for Seasonal Influenza ...

Do not use routine chemoprophylaxis for all exposed contacts. Prompt post-exposure prophylaxis within 48 hours with oseltamivir, zanamivir, laninamivir, or baloxavir probably reduces symptomatic influenza in people at high risk for severe disease, but does not achieve an important reduction among low-risk people in the same evidence synthesis.ScienceDirectScienceDirectAntivirals for post-exposure prophylaxis of influenza: a systematic review and network meta-analysis - ScienceDirect

Consider seasonal pre-exposure prophylaxis for adults and children aged 3 months or older at very high risk for complications when vaccination is contraindicated, unavailable, or expected to have low effectiveness, such as severely immunocompromised patients. Start when influenza activity is detected locally and continue for the duration of community activity; hematopoietic stem-cell transplant recipients in the first 6-12 months after transplant and lung-transplant recipients are specifically identified as candidates for consideration.PubMedPubMedClinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenza - PMC

For persons receiving pre-exposure prophylaxis who develop influenza-like symptoms, test for influenza and switch from prophylaxis to treatment dosing. If feasible, select an antiviral with a different resistance profile, provided there is no contraindication.PubMedPubMedClinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenza - PMC

If prophylaxis is used while a close contact of a high-risk person awaits vaccine response, continue it for 2 weeks after vaccination; children aged 6 months to under 9 years who require two vaccine doses need 6 weeks. Do not administer antiviral chemoprophylaxis for 2 weeks after live attenuated influenza vaccine.PubMedPubMedClinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenzaa

In long-term care facilities, begin antiviral treatment immediately for symptomatic residents during an outbreak assessment rather than waiting for trial-level certainty. Vaccinate unvaccinated staff and residents, but do not treat vaccination as an acute outbreak-control substitute because seroprotection requires approximately 14 days.WHOWHOPrevention and control of outbreaks of seasonal influenza ...

Reassess patients with progressive dyspnea, pneumonia, sepsis, worsening chronic cardiopulmonary disease, or inability to maintain oral intake because these syndromes shift management toward acute-care evaluation, oxygen and respiratory support when indicated, and treatment of the identified complication alongside influenza antiviral therapy.WHO+1WHOWHO EMRO - COVID-19 and influenzaPubMedInfluenza - CDC Yellow Book, 2026 edition - NCBI Bookshelf

In hospitalized patients with severe influenza, evidence from randomized trials remains uncertain for mortality and other major outcomes despite possible reductions in length of stay with oseltamivir or peramivir. This uncertainty supports prompt guideline-concordant treatment while maintaining active surveillance for bacterial pneumonia, respiratory failure, hemodynamic instability, and other causes of clinical deterioration rather than attributing worsening solely to influenza.The Lancet+2The LancetAntiviral treatment and prophylaxis for influenza - The LancetPubMedClinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal InfluenzaaPubMedInfluenza - CDC Yellow Book, 2026 edition - NCBI Bookshelf

If a patient receiving prophylaxis becomes symptomatic, obtain influenza testing and transition to treatment dosing rather than continuing prophylaxis dosing. For patients on oseltamivir or peramivir with impaired renal function, verify creatinine clearance before finalizing the regimen and revise dosing if renal function changes.PubMed+1PubMedClinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenza - PMCCDCInfluenza Antiviral Medications: Summary for Clinicians | Influenza (Flu) | CDC