• Influenza antiviral treatment is recommended for any patient with confirmed or suspected influenza who

    • is hospitalized

    • has severe, complicated, or progressive illness

    • is at high risk for complications or severe disease 

  • Consider antiviral treatment for any outpatient with confirmed or suspected influenza, regardless of rapid diagnostic testing results, if treatment can be initiated within 48 hours of illness onset

  • antiviral therapy should be started as soon as possible

    • ideally within 48 hours of symptoms

    • may be continued beyond 48 hours to benefit patients with severe, progressive, or complicated disease 

    • do not delay treatment while awaiting confirmatory test results

  • neuraminidase inhibitors are considered first-line therapy based on antiviral resistance patterns

  • oseltamivir 75 g orally twice daily for 5 days (consider oseltamivir 150 mg orally twice daily and longer treatment durations for immunocompromised patients)

  • zanamivir 10 mg (2 inhalations) twice daily for 5 days

  • peramivir 300 mg or 600 mg IV single dose

Infection control 

  • patients with influenza-like illness should remain isolated (out of school, work, and away from gatherings) until free of fever (100°F [37.8°C]) for ≥24 hours

  • patients in high-risk or healthcare settings may be encouraged to isolate for 7 days after symptom onset or until free of fever for ≥24 hours, whichever is longer

  • encourage good hand hygiene and respiratory etiquette

Risk factors for complicated or severe disease course 

  • high-risk conditions for increased risk of influenza complications include

    • children <5 years old, especially children <2 years old

    • adults ≥65 years old

    • pregnant women and women ≤2 weeks postpartum

    • persons with chronic medical conditions including
      • pulmonary disease including asthma

      • cardiovascular disease (except hypertension alone)

      • renal disease

      • hepatic disease

      • hematologic disease including sickle cell disease

      • metabolic disorders including diabetes mellitus

      • neurologic or neurodevelopment disorders

    • persons with immunosuppression due to medications or disease, such as HIV infection

    • persons <19 years old on long-term aspirin therapy (who might be at risk for Reye syndrome after influenza virus infection)

    • American Indians/Alaskan Natives

    • patients in chronic care facilities

    • persons with morbid obesity (BMI ≥40 kg/m2)


  • common complications include

    • pneumonia

    • otitis media

    • tracheobronchitis

    • acute sinusitis

    • exacerbations of chronic pulmonary or cardiac disease

  • less common complications include

    • Reye syndrome in children and adolescents taking aspirin

    • myocarditis

    • pericarditis

    • myositis

    • myoglobinuria

    • neurological sequelae
      • Guillain-Barré syndrome

      • transverse myelitis

      • encephalitis


  • uncomplicated influenza illness typically resolves after 3-7 days, but cough and malaise can persist >2 weeks


  • annual immunization for all individuals aged >6 months remains the most effective method of reducing influenza infection and related complications 

  • Post-exposure chemoprophylaxis

    • consider early treatment as alternative to chemoprophylaxis

    • consider postexposure prophylaxis with oseltamivir or zanamivir for higher-risk persons exposed to patients with influenza; this may be limited to patients in healthcare settings such as transplant units, neonatal units, or other patients with severe immunosuppression or other highly vulnerable patients

    • drug of choice for antiviral chemoprophylaxis is either oseltamivir or zanamivir, but monitor local antiviral resistance surveillance data.

Alan Drabkin, MD, is a senior clinical writer for DynaMed, a database of comprehensive updated summaries covering more than 3,200 clinical topics, and assistant clinical professor of population medicine at Harvard Medical School.