Update: Influenza Activity - United States, October 2, 2016-February 4, 2017.

This report summarizes U.S. influenza activity* during October 2, 2016-February 4, 2017, ^† and updates the previous summary (1). Influenza activity in the United States began to increase in mid-December, remained elevated through February 4, 2017, and is expected to continue for several more weeks. To date, influenza A (H3N2) viruses have predominated overall, but influenza A (H1N1)pdm09 and influenza B viruses have also been identified.