What is already known about this topic?
CDC collects, compiles, and analyzes data on influenza activity year-round in the United States. The influenza season generally begins in the fall and continues through the winter and spring months; however, the timing and severity of circulating influenza viruses can vary by geographic location and season.
What is added by this report?
During October 2–December 17, 2016, influenza activity remained low in October but has been slowly increasing since November in the United States. Influenza A (H3N2) viruses were the most frequently identified viruses. Almost all viruses characterized thus far this season have been similar to the components of the 2016–17 Northern Hemisphere trivalent and quadrivalent influenza vaccine formulations. All influenza viruses tested to date have been sensitive to the antiviral drugs oseltamivir, zanamivir, and peramivir.