Update: influenza activity - United States, September 28- December 6, 2014

Abstract

CDC collects, compiles, and analyzes data on influenza activity year-round in the United States (http://www.cdc.gov/flu/weekly/fluactivitysurv.htm). 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. Influenza activity in the United States increased starting mid-October through December. This report summarizes U.S. influenza activity during September 28-December 6, 2014.

FIGURE 1

Number* and percentage of respiratory specimens testing positive for influenza, by type, surveillance week, and year — U.S. World Health Organization and National Respiratory and Enteric Virus Surveillance System collaborating laboratories, United States, 2014–15 influenza season^† * N = 13,641. ^† Data reported as of December 12, 2014.

FIGURE 2

Percentage of all outpatient visits for influenza-like illness (ILI)* reported to CDC, by surveillance week — Outpatient Influenza-Like Illness Surveillance Network, United States, September 28–December 6, 2014, and selected previous influenza seasons^† * Defined as a fever (≥100°F [≥37.8°C]), oral or equivalent, and cough and/or sore throat, without a known cause other than influenza. ^† Data reported as of December 12, 2014.