Antiviral Use

Clinical benefit is greatest when antiviral treatment is administered early. When indicated, antiviral treatment should be started as soon as possible after illness onset, ideally within 48 hours of symptom onset. However, antiviral treatment might still have some benefits in patients with severe, complicated, or progressive illness and in hospitalized patients when started after 48 hours of illness onset.

Antiviral treatment with oseltamivir or zanamivir is recommended as early as possible for any patient with confirmed or suspected influenza who:

• is hospitalized;
• has severe, complicated, or progressive illness; or
• is at higher risk for influenza complications. This list includes:
• children aged younger than 2 years;
• adults aged 65 years and older;
• persons with chronic pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, hematological (including sickle cell disease), and metabolic disorders (including diabetes mellitus), or neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy [seizure disorders], stroke, intellectual disability [mental retardation], moderate to severe developmental delay, muscular dystrophy, or spinal cord injury);
• persons with immunosuppression, including that caused by medications or by HIV infection;
• women who are pregnant or postpartum (within 2 weeks after delivery);
• persons aged younger than 19 years who are receiving long-term aspirin therapy;
• American Indians/Alaska Natives;
• persons who are morbidly obese (i.e., body-mass index is equal to or greater than 40); and
• residents of nursing homes and other chronic-care facilities.

Clinical judgment, on the basis of the patient’s disease severity and progression, age, underlying medical conditions, likelihood of influenza, and time since onset of symptoms, is important when making antiviral treatment decisions for high-risk outpatients.Decisions about starting antiviral treatment should not wait for laboratory confirmation of influenza.

Oseltamivir is approved for treatment of influenza in persons aged two weeks and older, and for chemoprophylaxis to prevent influenza in people one year of age and older, while zanamivir is approved for treatment of persons seven years and older and for prevention of influenza in persons five years and older. Because high levels of resistance to adamantane antiviral medications continue to be observed among circulating influenza A viruses, adamantanes (rimantadine and amantadine) are not recommended for treatment or prevention of influenza.

Antiviral treatment also can be considered on the basis of clinical judgment for any previously healthy, symptomatic outpatient who is not considered “high risk” with confirmed or suspected influenza, if treatment can be initiated within 48 hours of illness onset.

Special Considerations for Institutional Settings

Use of antiviral chemoprophylaxis to control outbreaks among high risk persons in institutional settings is recommended. An influenza outbreak is likely when at least two residents are ill within 72 hours, and at least one has laboratory confirmed influenza. When influenza is identified as a cause of a respiratory disease outbreak among nursing home residents, use of antiviral medications for chemoprophylaxis is recommended for residents (regardless of whether they have received influenza vaccination) and for unvaccinated health care personnel. For newly-vaccinated staff, antiviral chemoprophylaxis can be administered up to two weeks (the time needed for antibody development) following influenza vaccination. Chemoprophylaxis may also be considered for all employees, regardless of their influenza vaccination status, if the outbreak is caused by a strain of influenza virus that is not well matched by the vaccine. Antiviral chemoprophylaxis should be administered for a minimum of two weeks, and continue for at least seven days after the last known case was identified.

To reduce the substantial burden of influenza in the United States, CDC continues to recommend a three-pronged approach:

(1) influenza vaccination. The influenza vaccine contains three or four influenzaviruses depending on the influenza vaccine—an influenza A (H1N1) virus, an influenza A (H3N2) virus, and one or two influenza B viruses. Therefore, even if vaccine effectiveness is reduced against drifted circulating viruses, the vaccine will protect against non-drifted circulating vaccine viruses. Further, there is evidence to suggest that vaccination may make illness milder and prevent influenza-related complications. Such protection is possible because antibodies created through vaccination with one strain of influenza viruses will often “cross-protect” against different but related strains of influenza viruses;

(2) use of neuraminidase inhibitor medications when indicated for treatment or prevention. Antiviral treatment with oseltamivir or zanamivir is recommended as early as possible for any patient with confirmed or suspected influenza who: is hospitalized; has severe, complicated, or progressive illness; or is at higher risk for influenza complications. Antiviral chemoprophylaxis should be used for prevention of influenza when indicated for institutional influenza outbreaks, and may be considered for those who have contraindications to influenza vaccination. CDC recommends antiviral chemoprophylaxis for a minimum of two weeks, and continuing for at least seven days after the last known case was identified.

(3) use of other preventive health practices that may help decrease the spread of influenza, including respiratory hygiene, cough etiquette, social distancing (e.g., staying home from work and school when ill, staying away from people who are sick) and hand washing.

For More Information:

• Influenza Vaccines Available in United States, 2014–15 Influenza Season:https://www.cdc.gov/flu/protect/vaccine/vaccines.htm
• Information for healthcare professionals on the use of influenza antiviral medications: https://www.cdc.gov/flu/professionals/antivirals/
• Summary of Influenza Antiviral Treatment Recommendations for clinicians: https://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm#summary
• Diagnostic Testing for Influenza: https://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm#diagnostic
• Interim Guidance for Influenza Outbreak Management in Long-Term Care Facilities: https://www.cdc.gov/flu/professionals/infectioncontrol/ltc-facility-guidance.htm

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  cdc, health alert, influenza