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

Abstract

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.

FIGURE 1

Number and percentage of respiratory specimens testing positive for influenza reported by clinical laboratories, by influenza virus type and surveillance week — United States, October 2, 2016–February 4, 2017 * 38,244 (9.7%) of 392,907 tested were positive during October 2, 2016–February 4, 2017.

FIGURE 2

Number of respiratory specimens testing positive for influenza reported by public health laboratories, by influenza virus type, subtype/lineage, and surveillance week — United States, October 2, 2016–February 4, 2017 * N = 15,781. ^† As of February 10, 2017.

FIGURE 3

Percentage of visits for influenza-like illness (ILI) reported to CDC, by surveillance week — Outpatient Influenza-Like Illness Surveillance Network, United States, 2016–17 influenza season and selected previous influenza seasons * Defined as fever (≥100°F [≥37.8°C]), oral or equivalent, and cough and/or sore throat, without a known cause other than influenza.