CDC Advises of Increase in Influenza A(H3N2) Activity
The U.S. Centers for Disease Control and Prevention (CDC) has issued a health advisory to notify clinicians that influenza activity remains high in the United States, with an increasing proportion of activity due to influenza A(H3N2) viruses, continued circulation of influenza A(H1N1) viruses, and low levels of influenza B viruses.
Influenza should be considered as a possible diagnosis for patients with respiratory illness while local influenza activity remains elevated. Because influenza A(H3N2) viruses may be associated with severe disease in older adults, the CDC’s health advisory should serve as a reminder that early empiric treatment with influenza antiviral medications is recommended for hospitalized and high-risk patients, especially those 65 years and older. Antiviral treatment should be started as soon as possible after illness onset and should not wait for laboratory confirmation.
Recommendations included in the Health Advisory include:
- Antiviral treatment is recommended as early as possible for any patient with suspected or confirmed influenza who:1) Is hospitalized—treatment is recommended for all hospitalized patients. 2) Has severe, complicated, or progressive illness—this may include outpatients with severe or prolonged progressive symptoms or patients who develop complications such as pneumonia but who are not hospitalized. 3) Is at high risk for influenza complications but not hospitalized.
- Clinical judgment—considering the patient’s disease severity and progression, age, likelihood of influenza, and time since onset of symptoms—is important when making antiviral treatment decisions for outpatients who are not at increased risk for influenza complications.
- Four influenza antiviral medications approved by the U.S. Food and Drug Administration (FDA) are recommended for use in the United States during the 2018-2019 influenza season: oseltamivir phosphate, zanamivir, peramivir, baloxavir marboxil.
- Clinical benefit is greatest when antiviral treatment is administered as early as possible after illness onset. Antiviral treatment should be started as soon as possible after illness onset and should not be delayed, even for a few hours to wait for the results of testing. Ideally, treatment should be initiated within 48 hours of symptom onset. However, antiviral treatment initiated later than 48 hours after illness onset can still be beneficial for some patients. Decisions about starting antiviral treatment should not wait for laboratory confirmation of influenza.
See the CDC’s Health Advisory for more specific details on medication dosing and treatment.
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