University of Wisconsin–Madison Medical College of Wisconsin

Decrease in Positivity Rate of Influenza Tests Coinciding With Outbreak of SARS-CoV-2: Data From a Southeastern Wisconsin Laboratory

Siddhartha Singh, MD, MS, MBA; Nathan A. Ledeboer, PhD; Purushottam W. Laud, PhD; Ryan Hanson, MS; Jonathon D. Truwit, MD, MBA

WMJ. 2020;119(4):275-277.

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Background: The SARS-CoV-2 outbreak prompted public health interventions and changes in public behavior that may have affected the 2019-2020 influenza season.

Methods: Using data from a laboratory in southeastern Wisconsin, we compared the number of weekly influenza tests and their positivity rates during the 2019-2020 influenza season with the previous 4 seasons.

Results: The number of influenza tests per week at the outset of the SARS-CoV-2 outbreak was higher than the average the previous 4 years, and positivity rates declined to 0% earlier than any of the previous 4 seasons.

Conclusion: The testing trajectory and positivity rate for influenza differed during the part of the 2019-2020 season coinciding with the SARS-CoV-2 outbreak as compared to similar periods during the previous 4 seasons.

Author Affiliations: Collaborative for Healthcare Delivery Sciences, Medical College of Wisconsin (MCW), Milwaukee, Wis (Singh, Laud, Hanson); Department of Pathology and Laboratory Medicine, MCW, Milwaukee Wis (Ledeboer); Division of Pulmonary and Critical Care Medicine, Department of Medicine, MCW, Milwaukee Wis (Truwit).
Corresponding Author: Siddhartha Singh MD, MS, MBA, 9200 W Wisconsin Ave, Milwaukee, WI 53226; phone 414.955.0289; email
Funding/Support: None declared.
Financial Disclosures: Dr Singh reports personal fees from Astra Zeneca, outside the submitted work.
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