Influenza Update

UPDATED: April 1, 2022

Influenza activity appears to be declining in Wisconsin and has resulted in a cumulative 354 hospitalizations for this season: 32 requiring ICU care, and 6 requiring mechanical ventilation.  Wisconsin has also recorded three pediatric influenza deaths.  Most detections have been A(H3N2).  Other than SARS-CoV-2 and influenza, we are seeing significant levels of human metapneumovirus and rhinovirus. 

Across the U.S. there have been 15,178 (2.2%) influenza detections at public health laboratories, from 697,940 specimens since October 3, 2021.  Of detected viruses, 99% have been influenza A and 1% have been influenza B.  Although H3N2 viruses have been genetically closely related to the vaccine virus, the interim estimate for vaccine effectiveness is very low: 14% (95% CI: -17—37).  The percentage of primary care patients with influenza-like illness has declined to 1.8% and is below baseline.  13 pediatric influenza-associated deaths have been reported in the U.S. since October 3, 2021.

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 continue to be confirmed using RT-PCR.

Influenza vaccination rates are lagging for Wisconsin compared to prior years, opening the door for more serious influenza outcomes.  Vaccinate!

Primary Care Snapshot

The most common viral cause of acute respiratory infections in Wisconsin, for the first time in a very long time is not SARS-CoV-2, but Rhinovirus!  For the week ending March 12, 2022, 2.5% of 44,111 specimens tested at the Wisconsin State Laboratory of Hygiene and clinical labs were positive for SARS-CoV-2.

Over the past 4 weeks the typical ARI case has been 32.9 years old. 52% of patients have been female. 46% of patients identified a sick contact 1-3 days before illness onset and they typically present to the clinic 5.0 days after illness onset. 66% of illnesses are characterized as mild, with 31% having moderate symptoms and 0% having severe symptoms.

Viruses in Circulation*Percent* in statewide laboratory surveillancePercent** in primary care surveillance clinics
Influenza A25.40.0
Influenza B0.30.0
Seasonal Coronavirus***0.814.0
*estimate based on WSLH statewide data
**estimate based on primary care patients seen at five clinics in Dane County where COVID-19 patients are often deflected
***includes HKU1, NL63, 229E and OC43

SARS-CoV-2 Cases

As of today, 487,661,811 global cases have been confirmed, with 6,141,720 reported deaths (CFR = 1.3%).  There have been 80,085,500 laboratory-confirmed cases reported in the United States with 980,557 deaths (CFR = 1.2%).  Closer to home, there have been 1,393,058 confirmed cases in Wisconsin, with 12,790 deaths (CFR = 0.9%).  Please note that the CFRs reported here are crude and based only on laboratory confirmed cases.


Across the state, case levels are increasing in 2 counties and declining in 1 of our 72 counties.  The transmission risk is high in 52 counties; 18 counties are at medium levels and 2 counties are at low levels.  The 7-day average for patients hospitalized for COVID-19 in Wisconsin is 202 and a 7-day average of 38 (19%) requiring intensive care. 

Wisconsin’s 14-day Trend

Over the past 14 days, there has been an increase in the growth rate of new cases per day (average of 9.5 additional new cases each day).

COVID-19 Vaccine

Wisconsin’s COVID-19 vaccine rollout continues with 9,387,225 doses administered as of 3/31/2022.  Across Wisconsin, 3,543,164 individuals (60.7% of the population) have completed their primary series of vaccine.  Booster and additional doses account for an additional 1,952,913 doses, suggesting that approximately 33.5% of our population is “up to date.” and 36% of our population is unvaccinated.

Wisconsin COVID-19 Vaccination Status
Up to DateFullyPartiallyUnvaccinated

Across the US:

- The overall cumulative rate for COVID-19 hospitalization across the U.S. is estimated at 958.2/100,000 (one admission for every 104 people). 

- The overall cumulative death rate for COVID-19 across the U.S. is 297.6/100,000 (one death for every 336 people). 

- 9.1% of all deaths during week 11 (Mar. 13—19) were due to pneumonia, influenza, or COVID-19.

- Variants: the national proportion of the Omicron variant was estimated to be 100% for the week ending March 26, 2022; 55% of the Omicron viruses are of the divergent BA.2 lineage. 

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:

Note:  two oral antiviral agents are available for treatment of COVID-19:


Molnupiravir (do not use in pregnancy):

* 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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