Atlanta—As 2017 begins, this year’s influenza season includes some good news so far, according to the CDC.
While it has been slowly increasing since November in the United States, flu activity remained low in October. Furthermore, most viruses characterized thus far this season have been similar to the components of the 2016-2017 Northern Hemisphere trivalent and quadrivalent influenza vaccine formulations. In addition, all influenza viruses tested to date have been sensitive to the antiviral drugs oseltamivir, zanamivir, and peramivir.
The CDC points out that peak influenza activity in the U.S. usually occurs from December through March, noting that substantial influenza activity can occur as early as November, and activity can last until May.
During the 2013-2014 and 2014-2015 influenza seasons, for example, documented flu cases began relatively early and peaked in late December and early January. During the 2015-2016 season, however, flu activity did not begin to increase until early January and peaked in mid-March.
“While it is not possible to predict when influenza activity will peak for the current season, influenza activity will likely increase in the coming weeks,” according to a recent update in the CDC’s Morbidity and Mortality Weekly Report.
The agency notes that, between October 2 and December 17, 2016, influenza A (H3N2) viruses were identified more frequently in the U.S. than other influenza viruses, but influenza A (H1N1)pdm09 and influenza B viruses were also reported. It adds that Influenza A (H3N2) virus–predominant seasons tend to be more severe overall than influenza A (H1N1)pdm09 virus–predominant seasons, with special concerns for the elderly and the very young.
The CDC also emphasizes that the majority of the influenza viruses collected in the U.S. since October 1, 2016, have been characterized antigenically or genetically as being similar to the reference viruses representing vaccine components recommended for the 2016-2017 Northern Hemisphere influenza vaccines.
“Annual influenza vaccination is the most effective method of preventing influenza and its complications. In the United States, during the 2010–11 through 2015–16 influenza seasons, influenza vaccination prevented an estimated 1.6 million to 6.7 million cases and 39,301–86,730 hospitalizations each season,” according to the report.
Yet, public health officials point out, as of early November, about 60% of the U.S. population had not been vaccinated against influenza for the 2016-2017 season. Overall influenza vaccination coverage during the 2015-2016 season was 45.6%, a 1.5 percentage point decrease compared with the 2014-2015 season. That decline as driven by decreased vaccine uptake among Americans aged 50-64 years and aged 65 or older.
“Because the peak month for influenza activity typically ranges from December to March, and influenza activity for the current season is just beginning to increase, receiving influenza vaccine at this time still offers substantial public health benefits,” according to the CDC, which urges pharmacists and other healthcare professionals to recommend influenza vaccine now and throughout the influenza season to all unvaccinated persons 6 months or older who do not have contraindications.
The agency also notes that all influenza viruses collected since October 1, and tested for antiviral resistance, were found to be susceptible to the available antiviral medications—oseltamivir, zanamivir, and peramivir.
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