Antiviral Treatment of Influenza: The Latest Guidelines

In this time of extreme climate phenomenon, I’d like to share with you regarding latest explanation from Dr. Alicia Fry, a physician with CDC’s Influenza Division, about recent lessons learned regarding influenza antiviral drugs and CDC’s treatment recommendations for the use of antiviral drugs during the 2010-2011 flu season.

In 2009-2010, the world experienced the first influenza pandemic in more than 40 years. And while the pandemic was less severe than many feared, millions of people in the United States became ill, hundreds of thousands were hospitalized, and thousands of people died. Studies prior to the 2009 H1N1 pandemic indicated that antiviral drugs were not commonly used by clinicians for influenza treatment, even among hospitalized patients. During the pandemic, CDC issued guidance on the use of antiviral agents promoting early and empiric treatment of severely ill persons and ill persons at high risk for complications from influenza and implemented clinician education and communications activities around this guidance. These efforts seem to have paid off. According to data from the Emerging Infections Program, which tracks reports of influenza-related hospitalizations in 10 states, approximately 80% of children and adults hospitalized with influenza infection received antiviral treatment during the pandemic.

The benefits of antiviral drugs have been documented for some time. In studies of previously healthy patients with uncomplicated influenza, treatment with neuraminidase inhibitor antiviral drugs (oseltamivir and zanamivir) reduced illness by 1-2 days and lessened illness severity.

However, prior to 2009, little information was available on the benefits of antiviral treatment among the severely ill (for example, hospitalized patients with flu) or among people at high risk for influenza complications, including pregnant women and people with certain underlying medical conditions. Several observational studies during the pandemic, however, showed that early treatment of more vulnerable populations was associated with a lower risk for serious influenza-related complications such as pneumonia, respiratory failure necessitating ICU admission, and death. In addition, data obtained during the pandemic indicate that when antiviral drugs are used to treat high-risk persons with 2009 H1N1 infection, they shortened the duration and reduced the severity of illness. Antiviral drugs were also shown to reduce the length of hospital stays.

Other studies found that hospitalized flu patients receiving antiviral treatment within 1-3 days of illness onset had significantly shorter periods of virus detection. In addition, some observational data strongly suggest that antiviral treatment among severely ill persons still had clinical benefit even if started more than 2 days after symptom onset.

Pregnant women were at greater risk for hospitalization and death from 2009 H1N1 infection. Several studies showed that treatment with antiviral drugs reduced the risk for ICU admission and death among pregnant women, especially when given within 2 days of symptom onset. However, benefits from antiviral drugs were still seen even when given up to 4 days after symptom onset.

While clinical judgment based on the patient’s disease severity and progression, age, underlying medical conditions, likelihood of influenza, and time since symptom onset is important to consider when making antiviral treatment decisions — the body of evidence available at this time has led CDC to recommend that, for the 2010-2011 influenza season, empiric antiviral treatment with the neuraminidase inhibitors oseltamivir (Tamiflu┬«) and zanamivir (Relenza┬«), be considered for a patient who:

  • Has severe, complicated, or progressive illness;
  • Is hospitalized; or
  • Is at higher risk for influenza complications, including pregnant women and people with certain underlying medical conditions.

When clinically indicated, influenza antiviral medications should be used to treat these most vulnerable patients as soon as possible, ideally (but not limited to) within 48 hours of symptom onset. Treatment should not wait for laboratory confirmation of influenza. Antiviral treatment can also be considered for any previously healthy, non-high-risk, symptomatic outpatient with confirmed or suspected influenza based upon clinical judgment, if treatment can be initiated within 48 hours of illness onset.

Influenza vaccination to prevent influenza infection and prompt antiviral therapy to treat influenza infection are the 2 most important medical countermeasures against the influenza viruses. Their correct application by healthcare professionals can provide life-saving benefits to patients.

For additional information about antiviral drug recommendations for the 2010-2011 influenza season, please visit For additional information, please visit the Emerging Infections Programs Web site. Thank you.

Web Resources

CDC Seasonal Influenza