Flu update - USA: Widespread in 37 states; Canada: Declining activities

January 27, 2017


According to the FluView report for the week ending January 21, 2017 (week 3), flu activity continues to increase in the United States. The number of states reporting widespread flu activity increased from 29 states to 37 states. Also, the Centers for Disease Control and Prevention (CDC) reported three additional flu-associated pediatric deaths for the 2016-2017 season. The proportion of people seeing their health care provider for influenza-like-illness (ILI) has been at or above the national baseline for six consecutive weeks so far this season.

Below is the summary of the report:

  • Viral Surveillance: The most frequently identified influenza virus subtype reported by public health laboratories during week 3 was influenza A (H3). The percentage of respiratory specimens testing positive for influenza in clinical laboratories increased.
  • 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: Three influenza-associated pediatric deaths were reported.
  • Influenza-associated Hospitalizations: A cumulative rate for the season of 15.4 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 3.4%, which is above the national baseline of 2.2%. All 10 regions reported ILI at or above their region-specific baseline levels. New York City and 10 states experienced high ILI activity; 10 states experienced moderate ILI activity; Puerto Rico and 17 states experienced low ILI activity; 13 states experienced minimal ILI activity, and the District of Columbia had insufficient data.

  • Geographic Spread of Influenza: The geographic spread of influenza in Puerto Rico and 37 states was reported as widespread; Guam and 12 states reported regional activity; the District of Columbia and one state reported local activity; and the U.S. Virgin Islands reported no activity.


In week 03, activity from several indicators including laboratory detections, outbreaks and hospitalizations declined from the previous week indicating that nationally the influenza season may have reached its peak in week 02.

A total of 2,667 positive influenza detections were reported in week 03, a decrease from the previous week.

A(H3N2) continues to be the most common type of influenza affecting Canadians.

The majority of cases, hospitalizations and deaths have been among adults aged 65+ years.

Sixty-six confirmed influenza outbreaks were reported in week 03, with the majority occurring in long-term care facilities and due to influenza A.

A total of 417 hospitalizations were reported by participating provinces and territories, down from 467 hospitalizations reported in the previous week.

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