During week 12 (March 18-24, 2018), influenza activity decreased in the United States.
April 1st, 2018During week 12 (March 18-24, 2018), influenza activity decreased in the United States.
- Viral Surveillance: Overall, influenza A(H3) viruses have predominated this season. However, in recent weeks the proportion of influenza A viruses has declined, and during week 12, influenza B viruses were more frequently reported than influenza A viruses. The percentage of respiratory specimens testing positive for influenza in clinical laboratories decreased.
- 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: Four influenza-associated pediatric deaths were reported.
- Influenza-associated Hospitalizations: A cumulative rate of 96.1 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 2.5%, which is above the national baseline of 2.2%. Nine of 10 regions reported ILI at or above region-specific baseline levels. Four states experienced high ILI activity; eight states experienced moderate ILI activity; New York City, Puerto Rico, the District of Columbia, and 14 states experienced low ILI activity; and 24 states experienced minimal ILI activity.
- Geographic Spread of Influenza: The geographic spread of influenza in Puerto Rico and 16 states was reported as widespread; 22 states reported regional activity; the District of Columbia, Guam and eight states reported local activity; four states reported sporadic activity; and the U.S. Virgin Islands reported no influenza activity.
