All data are preliminary and may change as more reports are received. Background: The Centers for Disease Control and Prevention’s (CDC) Influenza Division collects and analyzes influenza surveillance data year-round and produces a weekly report on U.S. influenza activity during the influenza season which begins at week 40 each year. The U.S. influenza surveillance system provides information in five categories collected from eight data sources. This is the first report of the 2012-2013 influenza season, which began on September 30, 2012, and also summarizes influenza activity during the summer weeks of the 2011-12 season. xternal_F1240.pdf

Stephen B. Thacker CDC Library collection