All data are preliminary and may change as more reports are received.
During week 10 (March 4-10, 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 10, the numbers of influenza A and influenza B viruses reported were similar. 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: Nine influenza-associated pediatric deaths were reported.
- Influenza-associated Hospitalizations: A cumulative rate of 89.9 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 3.3%, which is above the national baseline of 2.2%. All 10 regions reported ILI at or above region-specific baseline levels. Twelve states experienced high ILI activity; 13 states experienced moderate ILI activity; New York City and 14 states experienced low ILI activity; 11 states experienced minimal ILI activity; and Puerto Rico and the District of Columbia had insufficient data.
- Geographic Spread of Influenza: The geographic spread of influenza in Puerto Rico and 26 states was reported as widespread; Guam and 18 states reported regional activity; the District of Columbia and five states reported local activity; one state reported sporadic activity; and the U.S. Virgin Islands reported no activity.