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

Synopsis: During week 49 (December 6-12, 2015), influenza activity increased slightly in the United States but remained low overall.

• Viral Surveillance: The most frequently identified influenza virus type reported by public health laboratories during week 49 was influenza A, with influenza A (H1N1)pdm09 viruses predominating. The percentage of respiratory specimens testing positive for influenza in clinical laboratories was low.

• Novel Influenza A Virus: One human infection with a novel influenza A virus was reported.

• 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: No influenza-associated pediatric deaths were reported.

• Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 1.9%, which is below the national baseline of 2.1%. Four 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; New York City and two states experienced low ILI activity; 46 states experienced minimal ILI activity; and the District of Columbia had insufficient data.

• Geographic Spread of Influenza: The geographic spread of influenza in Guam was reported as widespread; Puerto Rico and two states reported regional activity; 12 states reported local activity; the District of Columbia, the U.S. Virgin Islands, and 33 states reported sporadic activity; and three states reported no influenza activity.

External_F1549.pdf

Stephen B. Thacker CDC Library collection

United States