When to Give Antiviral Drugs for the Flu

Angela J.P. Campbell, MD, MPH


March 17, 2014

Editorial Collaboration

Medscape &

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Hello. I am Angela Campbell, a physician in the Influenza Division at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia. I am happy to speak with you today as part of the CDC Expert Commentary Series on Medscape.

To date this flu season, influenza A (H1N1) viruses have caused most of the laboratory-confirmed flu illnesses and hospitalizations. This is the H1N1 virus that has circulated each year as a seasonal influenza virus since it emerged and caused a pandemic in 2009. Although flu season is often hardest on the very old and very young, this season, most hospitalizations -- roughly 60% -- have occurred in people 18-64 years old. CDC continues to recommend annual vaccination as the best tool for preventing influenza, and early and empirical use of antiviral medications to treat influenza infection in certain patients.

Evidence from past influenza seasons and the 2009 H1N1 pandemic has shown that treatment with antiviral medications can have clinical and public health benefit in reducing severe outcomes of influenza when initiated soon after illness onset. Clinical trials and observational data show that early antiviral treatment may:

Shorten the duration of fever and illness symptoms;

Reduce the risk for complications and death; and

Shorten the duration of hospitalization.

Clinical benefit is greatest when antiviral treatment is initiated early. When indicated, antiviral treatment should be started as soon as possible after illness onset -- ideally, within 48 hours of symptom onset. However, observational studies show that antiviral treatment might still be beneficial in patients with severe, complicated, or progressive illness, and in hospitalized patients when started even later than 48 hours after illness onset.

In summary, antiviral treatment 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.

Persons at higher risk for influenza complications in whom antiviral treatment is recommended include children younger than 2 years of age, adults aged 65 and older, persons with certain medical conditions, pregnant or postpartum women, American Indians and Alaskan Natives, and residents of nursing homes and other chronic-care facilities.

Decisions about starting antiviral treatment should not wait for test results or laboratory confirmation of influenza. When there is clinical suspicion of influenza and antiviral treatment is indicated, antiviral treatment should be started as soon as possible, along with use of appropriate infection control measures.

Lastly, clinicians can use their clinical judgment and consider antiviral treatment for previously healthy outpatients with confirmed or suspected influenza who are not in one of the high-risk groups, if treatment can be initiated within 48 hours of illness onset.

The antiviral medications that are currently recommended for treatment of influenza are oral oseltamivir and inhaled zanamivir. Of the flu viruses tested for resistance to date, the vast majority have been susceptible to both medications. For outpatients, treatment with either medication is recommended, although oral oseltamivir is preferentially recommended for pregnant women. For hospitalized patients and patients with severe or complicated illness, treatment with oral oseltamivir is recommended. Inhaled zanamivir is not recommended for use in patients with severe influenza disease. Complete guidance on dosage and duration of treatment using US Food and Drug Administration (FDA)-approved medications, as well as current information on investigational antivirals, such as intravenous zanamivir, is available on the CDC Website. Check out the resources on this page for more information. Thank you.

Web Resources: CDC

Influenza (Flu) Information for Health Professionals

Prevention and Control of Seasonal Influenza With Vaccines

Antiviral Drugs

Influenza Antiviral Medications: Summary for Clinicians

Angela J.P. Campbell, MD, MPH, is a Medical Officer for the Epidemiology and Prevention Branch in the Influenza Division in CDC's National Center for Immunization and Respiratory Diseases. Dr. Campbell earned her Doctor of Medicine at Vanderbilt University in 1999, and completed training in pediatrics and pediatric infectious diseases at the University of Washington. She also completed the Epidemic Intelligence Service training at CDC, and obtained a Master of Public Health in Epidemiology from the University of Washington School of Public Health. Board-certified in pediatrics and pediatric infectious diseases, Dr. Campbell was a fellow and faculty member in Seattle for 9 years in the Department of Pediatrics at the University of Washington before rejoining CDC in March 2013.

Dr. Campbell's clinical and research interests over the past decade have focused on factors that influence the acquisition of respiratory virus infection and disease progression among immunocompromised children and adults, with the goal of facilitating new diagnostic, preventive, and treatment strategies for respiratory virus infections. Her current primary research focuses on studies of influenza antiviral treatment and antiviral effectiveness, and she is responsible for developing and revising the CDC clinical guidance related to treatment and prevention of seasonal and novel influenza viruses.

Dr. Campbell is an Affiliate Investigator in the Vaccine and Infectious Disease Division at the Fred Hutchinson Cancer Research Center in Seattle. She is also an Adjunct Assistant Professor of Pediatrics at Emory University School of Medicine, and has an active professional staff appointment at Children's Healthcare of Atlanta.