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Influenza Activity in the US During 2016-17 Season

MMWR; ePub 2017 Jun 30; Blanton, et al

Publish date:

During the 2016-17 influenza season in the US, the circulation of influenza A (H3N2) viruses was predominant, with influenza activity peaking in mid-February, according to a recent CDC study that examined influenza activity in the US during the 2016-17 season and composition of the 2017-18 influenza virus. The report also found:

  • Influenza activity remained low through November 2016, increased during December, and peaked in February.
  • During October 2, 2016 to May 20, 2017, influenza A (H3N2) viruses were identified most frequently, but influenza A (H1N1)pdm09 and influenza B viruses were also reported.
  • Influenza vaccination this season reduced the overall risk for influenza-associated medical visits by 42%.
  • The composition of the 2017-18 influenza vaccine had been updated to better match circulating influenza viruses.

Citation:

Blanton L, Alabi N, Mustaquim D, et al. Update: Influenza activity in the United States during the 2016–17 season and composition of the 2017–18 influenza vaccine. MMWR Morb Mortal Wkly Rep. 2017;66:668–676. doi:10.15585/mmwr.mm6625a3.

Commentary:

During 2016-2017, influenza A(H3N2) virus was the predominant influenza virus in circulation. Typically, influenza A(H3N2) predominant seasons are associated with high rates of hospitalizations and deaths compared with seasons that are not influenza A(H3N2), and this season fits that pattern. Importantly, there was no new emergence of antiviral resistance, and all isolates were susceptible to oseltamivir, zanamivir, and peramivir. Interestingly, while a 42% decrease in influenza-related medical visits may seem less than one thought, in an analysis of the 2012–13 season, with an estimated vaccination effectiveness against A(H3N2)-related illness of 39%, vaccination was estimated to have avoided 5.6 million illnesses, 2.7 million medical visits, 61,500 hospitalizations, and 1,800 deaths.1 Annual influenza vaccination remains the recommendation for all persons aged ≥6 months of age. —Neil Skolnik, MD

  1. Centers for Disease Control and Prevention. Estimated influenza illnesses, medical visits, hospitalizations, and deaths averted by vaccination in the United States. US Department of Health and Human Services, CDC; 2017. https://www.cdc.gov/flu/about/ disease/2015-16.htm. Accessed July 8, 2017.

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