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

During week 12 (March 19-25, 2017), influenza activity remained elevated in the United States.

• Viral Surveillance: The most frequently identified influenza virus subtype reported by public health laboratories during week 12 was influenza A (H3). The percentage of respiratory specimens testing positive for influenza in clinical laboratories increased slightly.

• Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was above the system-specific epidemic threshold in the National Center for Health Statistics (NCHS) Mortality Surveillance System.

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

• Influenza-associated Hospitalizations: A cumulative rate for the season of 54.1 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 3.2%, which is above the national baseline of 2.2%. Eight of ten regions reported ILI at or above their region-specific baseline levels. 10 states experienced high ILI activity; eight states experienced moderate ILI activity; eight states experienced low ILI activity; New York City, Puerto Rico, and 24 states experienced minimal ILI activity; and the District of Columbia had insufficient data.

• Geographic Spread of Influenza: The geographic spread of influenza in 31 states was reported as widespread; Guam, Puerto Rico and 12 states reported regional activity; the District of Columbia and five states reported local activity; two states reported sporadic activity; and the U.S. Virgin Islands reported no activity.

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