FluView : 2017-2018 influenza season week 4 ending January 27, 2018

All data are preliminary and may change as more reports are received.During week 50 (December 10-16, 2017), influenza activity sharply increased in the United States.During week 4 (January 21-27, 2018), influenza activity increased in the United States.\u2022 Viral Surveillance: The most frequently identified influenza virus subtype reported by public health laboratories during week 4 was influenza A(H3). The percentage of respiratory specimens testing positive for influenza in clinical laboratories remained elevated.\u2022 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.\u2022 Influenza-associated Pediatric Deaths: Seventeen influenza-associated pediatric deaths were reported, one of which occurred during the 2015-2016 season.\u2022 Influenza-associated Hospitalizations: A cumulative rate of 51.4 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported.\u2022 Outpatient Illness Surveillance:The proportion of outpatient visits for influenza-like illness (ILI) was 7.1%, which is above the national baseline of 2.2%. All 10 regions reported ILI at or above region-specific baseline levels. New York City, the District of Columbia, and 42 states experienced high ILI activity; Puerto Rico and two states experienced moderate ILI activity; three states experienced low ILI activity; and three states experienced minimal ILI activity.\u2022 Geographic Spread of Influenza:The geographic spread of influenza in Puerto Rico and 48 states was reported as widespread; Guam and one state reported regional activity; the District of Columbia and one state reported local activity; and the U.S. Virgin Islands reported sporadic activity.2018713