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

Synopsis: During week 1 (January 3-9, 2016), laboratory data indicated that influenza activity increased slightly in the United States.

• Viral Surveillance: The most frequently identified influenza virus type reported by public health laboratories during week 1 was influenza A, with influenza A (H1N1)pdm09 viruses predominating. The percentage of respiratory specimens testing positive for influenza in clinical laboratories was low.

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

• Influenza-associated Pediatric Deaths: One influenza-associated pediatric death was reported.

• Influenza-associated Hospitalizations: A cumulative rate for the season of 1.5 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 2.0%, which is below the national baseline of 2.1%. Four of 10 regions reported ILI at or above region-specific baseline levels. Puerto Rico and one state experienced high ILI activity; New York City and seven states experienced low ILI activity; 42 states experienced minimal ILI activity; and the District of Columbia had insufficient data.

• Geographic Spread of Influenza: The geographic spread of influenza in Guam, Puerto Rico, and nine states were reported as regional; 11 states reported local activity; the U.S. Virgin Islands and 28 states reported sporadic activity; and the District of Columbia and two states reported no influenza activity.

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