Traditional definition underestimates burden of health care-associated flu
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Using a traditional definition of health care-associated influenza missed more than 80% of possible cases among patients admitted to acute-care hospitals during seven influenza seasons, researchers reported at the SHEA Spring Conference.
“Traditional definitions of health care-associated viral infections, including influenza, often just examine and/or include cases that could be due to health care exposure in the hospital, but they fail to recognize that infections diagnosed on admission to the hospital — community cases — may have other associated health care exposures, like recent nursing home, hospital or other health care facility visits,” Thomas R. Talbot, MD, MPH, professor of medicine and chief hospital epidemiologist at Vanderbilt University Medical Center, told Healio.
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For their study, Talbot, Erin Gettler, MD, and colleagues assessed laboratory-confirmed cases of influenza among adult and pediatric patients who were admitted to any acute-care hospital in eight Tennessee counties between Oct. 1, 2012, and April 30, 2019.
They compared results when using a traditional definition of health care-associated influenza — laboratory confirmation of infection on or after hospital day 4 — or an enhanced definition, in which lab confirmation came between hospital days 0 and 3 in patients who were transferred from a chronic care facility or with a recent discharge from another acute-care facility in the 7 days preceding the current index admission.
Overall, there were 5,904 cases of laboratory-confirmed influenza among hospitalized patients during the study period. Using the traditional definition revealed 147 cases of health care-associated influenza, whereas using the enhanced definition revealed an additional 317 cases among patients transferred from a long-term care facility and 336 among patients with a prior acute-care facility admission in the preceding 7 days.
According to the researchers, using their expanded definition, the total number of health care-associated influenza infections in the cohort was 772, only 19% of which were captured using the traditional definition.
“Health care-associated viral infections are important nosocomial infections that are underrecognized,” Talbot said. “Surveillance for health care-associated influenza should include metrics that capture health care exposures outside of the concurrent acute-care hospitalization.”
Talbot said the lack of an influenza season this year due to mitigation efforts for the pandemic could have an impact on this type of research going forward. However, he anticipates that influenza will not stay in the background much longer and will likely re-emerge as COVID-19 rates reduce.
Additionally, Talbot said the 2020-2021 influenza season should include an asterisk or be excluded from studies because of the dramatic reduction in influenza activity across the world.
“However, given the usual morbidity and mortality from influenza, this is a good problem to have given those reductions in harm,” he said.
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Gettler E, et al. Traditional definition of healthcare-associated influenza underestimates cases associated with other healthcare exposures. Presented at: SHEA Spring 2021 Conference; April 13-16, 2021 (virtual meeting).
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