Influenza Update

UPDATED: December 2, 2021

Wisconsin has experienced a significant increase in influenza detections over the past week, although it continues to be at relatively low activity.  Detections have been predominantly A(H3N2) and may have accelerated due to Thanksgiving travel.  Other than SARS-CoV-2, we are seeing significant levels of rhinoviruses and RSV.  Wisconsin recorded no influenza deaths for the entire 2020-2021 season or for this season.  This shows the incredible power of public health measures for influenza control.


Across the U.S. there have been 777 (0.5%) influenza detections at public health laboratories, from 141,516 specimens, since October 3, 2021.  Of detected viruses, 95% have been influenza A and 5% have been influenza B.  The percentage of primary care patients with influenza-like illness has not been above baseline since March 2020, and there has been only one pediatric influenza-associated death reported in the U.S. since September 27, 2020. 


Use of rapid testing at this time is limited by the low levels of influenza and the increased risk for false positives.  RIDT (+) results should be confirmed using RT-PCR.

Primary Care Snapshot

The most commonly identified viral cause of acute respiratory infections in Wisconsin is SARS-CoV-2.  For the week ending November 29, 2021, 10.4% of 84,334 specimens tested at the Wisconsin State Laboratory of Hygiene and clinical labs were positive for SARS-CoV-2.

Viruses in Circulation*Percent
Influenza A1.3
Influenza B0.1
Seasonal Coronavius**0.0
*estimate based on WSLH statewide data
** includes HKU1, NL63, 229E and OC43

SARS-CoV-2 Cases

As of today, 263,689,974 global cases have been confirmed, with 5,228,097 reported deaths (CFR = 2.0%).  There have been 48,695,518 laboratory-confirmed cases reported in the United States with 782,106 deaths (CFR = 1.6%).  Closer to home, there have been 879,614 confirmed cases in Wisconsin, with 9,052 deaths (CFR = 1.0%).  Please note that the CFRs reported here are crude and based only on laboratory confirmed cases.


We are seeing ongoing, high levels of SARS-CoV-2 transmission.  The 7-day average for patients hospitalized for COVID-19 in Wisconsin is 1,336 and a 7-day average of 364 (27%) requiring intensive care.

Wisconsin’s 14-day Trend

Over the past 14 days, there has been a slight decline in the growth rate of new cases per day (2.7 fewer cases each day), likely driven by reduced testing over Thanksgiving.

COVID-19 Vaccine

Wisconsin’s COVID-19 vaccine rollout continues with 7,697,130 doses administered as of 12/01/2021.  Across Wisconsin, 3,266,637 individuals (56.1% of the population) are now fully vaccinated. 

Across the US:

- The estimated overall cumulative rate for COVID-19 hospitalization across the U.S. is 745.2/100,000 (one admission for every 134 people). 


- The overall cumulative death rate for COVID-19 across the U.S. is 237.3/100,000 (one death for every 421 people). 


-14.5% of deaths during week 46 (November 14 – November 20) were due to pneumonia, influenza or COVID-19.


- Variants: the national proportion of the Delta variant is estimated to be greater than 99.9%.  The Omicron variant (B.1.1.529) has now been detected in the United States.

Please refer to guidance provided by Wisconsin Department of Health Services, available at:

and by the U.S. Centers for Disease Control and Prevention, available at:

* The weekly influenza update is adapted from an email from Jon Temte, MD, PhD; Chair, Wisconsin Council on Immunization Practices; Professor, Department of Family Medicine and Community Health, University of Wisconsin School of Medicine and Public Health.

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