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New Tools for a Harsh Flu Season

Amesh A. Adalja, MD, FACP, FACEP, January 9, 2015

As has become apparent, this year’s influenza season will be particularly harsh because of the predominance of an H3N2 strain that is not included in the current vaccine. The vaccine mismatch heightens the importance of recognizing influenza and treating it with antivirals. This season, clinicians will have 2 new tools to help with this task.

Intravenous Antiviral Approved

Historically, antiviral treatment for influenza has been exclusively via the oral or inhalational route. For ordinary cases of influenza, the oral route of administration has not been a challenge, but for severe cases, in which oral absorption and bioavailability cannot be ensured, an intravenous (IV) formulation was desired. During the 2009 H1N1 pandemic, this need was met through the issuance by the FDA of an emergency use authorization for IV peramivir and compassionate use of IV zanamivir, both neuraminidase class antivirals. Since the time of the pandemic, however, no FDA-approved IV formulations have existed. 

Earlier this season, the first IV influenza antiviral, peramivir, was approved by the FDA. The efficacy trial that led to its approval was based on achieving clinical endpoints that included resolution of symptoms and fever. Importantly, efficacy was not established in hospitalized patients.1 Peramivir also has the advantage of requiring only a single dose.

Clinical guidance from hospitals and professional societies will now need to reflect this new treatment’s availability and recommend which patients should be treated with peramivir and which should receive oral oseltamivir or inhaled zanamivir. 

Molecular Diagnostic Test CLIA-Waived

The diagnosis of influenza has often been hampered by the lack of availability of a rapid and sensitive test. Traditional point-of-care testing has been based on rapid antigen tests that have been plagued with poor sensitivity, leading to many false-negative results. Until the advent of molecular PCR-based assays, alternatives included time-consuming viral culture and immunofluorescence. PCR tests, however, had been deemed too complex to be performed at the bedside and were relegated to hospital laboratories, where turnaround time could prove to be prohibitive for ambulatory patients. 

The clearance and CLIA waiver issued for a rapid PCR-based influenza test (Alere i Influenza A&B)—the first molecular test to receive a CLIA waiver—will allow clinicians to rule out and diagnose influenza in a rapid manner with much more certainty.2 It remains to be seen what the uptake of this test will be in emergency departments, doctors’ offices, and urgent care clinics and how it will be used in conjunction with multiplex respiratory virus assays that are increasingly being employed in hospitalized patients

Treating Influenza in the 21st Century

The recognition of influenza as an important infectious disease threat and the increased awareness that clinicians require an adequate armamentarium of antivirals, diagnostics, and vaccines is a particularly important development. As clinicians become more accustomed to using all these tools, more effective management of influenza should result.

 

References

  1. FDA approves Rapivab to treat flu infection [news release]. December 22, 2014. US Food and Drug Administration website. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm427755.htm. Accessed January 7, 2015.
  2. FDA grants first CLIA waiver for nucleic acid-based flu diagnostic test [news release]. January 6, 2015. US Food and Drug Administration website. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm429127.htm. Accessed January 7, 2015.