A new study based on pre–COVID-19-pandemic data from nine US states shows that all-cause mortality burden is substantial among patients hospitalized with flu. The study is published in Clinical Infectious Diseases. 

The study collected data from the 2010-11 through 2018-19 seasons from the Influenza Hospitalization Surveillance Network, then linked flu cases to death certificates to find patients who died from any cause during their influenza hospital stay or within 30 days post discharge.

In total, among 121,390 patients hospitalized with laboratory-confirmed influenza over 9 seasons, 5.5% of case-patients died. And 48% of deaths occurred within 30 days of hospital discharge. The average time between discharge and death was 9 days.

Among those who died, 76% were age 65 years or older, and 71% were non-Hispanic White. 

Older adults carry residual risk of death 

Only 37% of deaths had "influenza" on their death certificate, the authors said. 

"Among patients that died post-discharge, 36.9% were discharged to a nursing home or long-term care facility, 36.7% to hospice, and 23.3% to a private residence," the authors said. 

Patients who died within a month of hospital discharge were more likely to have one or more of several underlying health conditions, including cardiovascular disease, chronic lung disease, immunosuppressive conditions, chronic metabolic disease and neurologic disease.

Medical providers should be aware of the residual risk for mortality soon after discharge from an influenza-associated hospitalization, particularly among older adults.

"Medical providers should be aware of the residual risk for mortality soon after discharge from an influenza-associated hospitalization, particularly among older adults," the authors concluded. "Influenza surveillance systems should consider capture of post-discharge outcomes to better characterize immediate and short-term impacts of influenza on morbidity and mortality."