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You missed a few: a better way to count health care-associated influenza cases

Dec. 8, 2023, 10:00 AM

by Paul Govern

The traditional definition of health care-associated influenza leads to gross undercounting, a recent study suggests. 

As reported in Infection Control & Hospital Epidemiology, Erin Gettler, MD, Thomas Talbot, MD, MPH, and colleagues analyzed data on 5,904 patients from eight counties in Middle Tennessee who were hospitalized with influenza from 2012 to 2019. Only 147 cases, or 2.5%, met the traditional definition of health care-associated influenza, with a positive test result coming after hospital day three.  

However, when the researchers included patients testing positive in the first three days who were transferred from post-acute care facilities or discharged from hospitalization for non-influenza illness within the previous seven days, they identified an additional 1,031 health care-associated cases.  

In total, 20% of influenza hospitalizations were considered health care-associated using this expanded definition — eight times higher than estimates based on the traditional definition. Standardizing surveillance methodology to include preadmission health care exposures allows better estimation of the burden of health care-associated influenza and will help inform policies to prevent influenza transmission in health care facilities, the authors write. 

Gettler, a former resident and fellow at Vanderbilt University Medical Center, is now at Duke University. Others on the study from VUMC include H. Keipp Talbot, MD, MPH, Yuwei Zhu, MD, MS, Danielle Ndi, MPH, Edward Mitchel MS, Tiffanie Markus, PhD, William Schaffner, MD, and Bryan Harris MD, MPH. The study was supported in part by the National Institutes of Health (UL1TR002243). 

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