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 13 (March 25-31, 2012), influenza activity was elevated in some areas of the United States, but declined nationally and in most regions.

• U.S. Virologic Surveillance: Of the 4,551 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, 932 (20.5%) 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: One influenza-associated pediatric death was reported and was associated with an influenza A virus for which the subtype was not determined.

• Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 1.7%, which is below the national baseline of 2.4%. All regions reported ILI below region-specific baseline levels. Six states experienced low ILI activity; New York City and 44 states experienced minimal ILI activity, and the District of Columbia had insufficient data to calculate ILI activity.

• Geographic Spread of Influenza: Ten states reported widespread geographic activity; 19 states reported regional influenza activity; 13 states reported local activity; the District of Columbia, Guam, Puerto Rico, and 8 states reported sporadic activity, and the U.S. Virgin Islands reported no influenza activity.

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