federal health officials said.
Officials at the Centers for Disease Control and Prevention said for the week ending April 28, of the 2,886 specimens tested by U.S. World Health Organization and National Respiratory and Enteric Virus Surveillance System collaborating laboratories, 15.3 percent were positive for influenza.
The proportion of deaths attributed to pneumonia and influenza was below the epidemic threshold.
However, two influenza-associated pediatric deaths were reported. One case was associated with the 2009 H1N1 virus and one was associated with a seasonal influenza A (H3) virus.
The proportion of outpatient visits for influenza-like illness was 1.1 percent.
Alabama, Alaska, Hawaii, and Washington state reported low influenza-like illness, while 46 states experienced minimal influenza-like illness activity, the CDC said. The District of Columbia had insufficient data to calculate influenza-like illness activity.
Less than 50 percent of U.S. influenza B viruses tested this season are similar to the influenza B component in this year's influenza vaccine, and influenza B viruses account for only 10 percent of influenza positive tests reported to CDC this season, officials said.