All data are preliminary and may change as more reports are received.

Synopsis: During week 15 (April 10-16, 2016), influenza activity decreased in the United States.

• Viral Surveillance: The most frequently identified influenza virus type reported by public health laboratories during week 15 was influenza A, with influenza A (H1N1)pdm09 viruses predominating. The percentage of respiratory specimens testing positive for influenza in clinical laboratories decreased.

• Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was below the system-specific epidemic threshold in the NCHS Mortality Surveillance System and above the system-specific epidemic threshold in the 122 Cities Mortality Reporting System.

• Influenza-associated Pediatric Deaths: Six influenza-associated pediatric deaths were reported.

• Influenza-associated Hospitalizations: A cumulative rate for the season of 28.4 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported.

• Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 2.1%, which is at the national baseline of 2.1%. Five of 10 regions reported ILI at or above region-specific baseline levels. One state experienced high ILI activity; Puerto Rico and one state experienced moderate ILI activity; 11 states experienced low ILI activity; New York City and 37 states experienced minimal ILI activity; and the District of Columbia had insufficient data.

• Geographic Spread of Influenza: The geographic spread of influenza in Puerto Rico and 14 states was reported as widespread; Guam and 19 states reported regional activity; the District of Columbia and 13 states reported local activity; and the U.S. Virgin Islands and four states reported sporadic activity.

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