Synopsis: During week 13 (March 29-April 4, 2015), influenza activity continued to decrease in the United States.

o ViralSurveillance:Of10,684specimenstestedandreportedbyU.S.WorldHealth Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 13, 1,138 (10.7%) were positive for influenza.

o PneumoniaandInfluenzaMortality:Theproportionofdeathsattributedtopneumoniaand influenza (P&I) was below the epidemic threshold.

o Influenza-associatedPediatricDeaths:Twoinfluenza-associatedpediatricdeathswere reported.

o Influenza-associatedHospitalizations:Acumulativeratefortheseasonof61.1 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported.

o OutpatientIllnessSurveillance:Theproportionofoutpatientvisitsforinfluenza-likeillness (ILI) was 1.8%, which is below the national baseline of 2.0%. Five regions reported ILI at or above region-specific baseline levels. Puerto Rico experienced moderate ILI activity; seven states experienced low ILI activity; New York City and 43 states experienced minimal ILI activity; and the District of Columbia had insufficient data.

o GeographicSpreadofInfluenza:Thegeographicspreadofinfluenzainfourstateswas reported as widespread; 17 states reported regional activity; the District of Columbia, Guam, and 22 states reported local activity; and Puerto Rico, the U.S. Virgin Islands, and seven states reported sporadic activity.

Stephen B. Thacker CDC Library collection

United States