National Center for Immunization and Respiratory Diseases (U.S.). Influenza Division.

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

Synopsis: During week 12 (March 18-24, 2012), influenza activity was elevated in some areas of the United States, but remained relatively low nationally.

• U.S. Virologic Surveillance: Of the 4,624 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division, 908 (19.6%) were positive for influenza.

• Pneumonia and Influenza (P&I) Mortality Surveillance: The proportion of deaths attributed to P&I was below the epidemic threshold.

• Influenza-associated Pediatric Mortality: Four influenza-associated pediatric deaths were reported and were associated with 1 2009 H1N1 and 3 influenza A viruses for which the subtype was not determined.

• Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 2.0%, which is below the national baseline of 2.4%. Regions 5 and 10 reported ILI above region-specific baseline levels. Three states experienced moderate ILI activity; 6 states experienced low ILI activity; New York City and 41 states experienced minimal ILI activity, and the District of Columbia had insufficient data to calculate ILI activity.

• Geographic Spread of Influenza: Sixteen states reported widespread geographic activity; 21 states reported regional influenza activity; 9 states reported local activity; the District of Columbia, Guam, Puerto Rico, and 4 states reported sporadic activity, and the U.S. Virgin Islands reported no influenza activity.

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