Weekly U.S. Influenza Surveillance ReportFull report also available as PDF
2016-2017 Influenza Season Week 18 ending May 6, 2017
All data are preliminary and may change as more reports are received.
During week 18 (April 30-May 6, 2017), influenza activity decreased in the United States.
- Viral Surveillance: The most frequently identified influenza virus type reported by public health laboratories during week 18 was influenza B. 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 below the system-specific epidemic threshold in the National Center for Health Statistics (NCHS) Mortality Surveillance System.
- Influenza-associated Pediatric Deaths: Two influenza-associated pediatric deaths were reported.
- Influenza-associated Hospitalizations: A cumulative rate for the season of 64.3 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 1.6%, which is below the national baseline of 2.2%. All ten regions reported ILI below their region-specific baseline levels. One state experienced low ILI activity; New York City, Puerto Rico, and 49 states experienced minimal ILI activity; and the District of Columbia had insufficient data.
- Geographic Spread of Influenza: The geographic spread of influenza in one state was reported as widespread; Guam and seven states reported regional activity; Puerto Rico and 14 states reported local activity; the District of Columbia and 28 states reported sporadic activity; and the U.S. Virgin Islands reported no activity.