Widespread activity, meaning 50 percent of geographic regions in a state reporting flu activity, was reported in Alabama, Alaska, Kansas, Louisiana, Massachusetts, New York, Pennsylvania, Texas, Virginia and Wyoming.
In the previous week, only Alabama, Louisiana, New York and Texas reported widespread flu. Widespread activity only looks at the spread of the illness and not its severity.
So far, "it's a typical influenza season, if I can use that word," said Dr. Michael Jhung, a medical officer in the CDC's flu division.
The H1N1 strain of the flu, which caused a pandemic in 2009, is the most common this year. At that time it was called swine flu, but according to Jhung the virus has adapted to the human population and is now known as a human seasonal virus.
Four pediatric flu deaths have been reported since September 29, but the CDC does not track or monitor adult flu-related deaths.
Swim Week Miami Beach 2014 [PHOTOS]