The Burden of All-Cause Mortality Following Influenza-Associated Hospitalizations: Influenza Hospitalization Surveillance Network, 2010-2019.

backgroundWhile the estimated number of US influenza-associated deaths is reported annually, detailed data on the epidemiology of influenza-associated deaths, including the burden of in-hospital vs post-hospital discharge deaths, are limited.

methodsUsing data from the 2010-2011 through 2018-2019 seasons from the Influenza Hospitalization Surveillance Network, we linked cases to death certificates to identify patients who died from any cause during their influenza hospital stay or within 30 days post discharge. We described demographic and clinical characteristics of patients who died in the hospital vs post discharge and characterized locations and causes of death (CODs).

resultsAmong 121 390 cases hospitalized with laboratory-confirmed influenza over 9 seasons, 5.5% died; 76% of deaths were in patients aged ≥65 years, 71% were non-Hispanic White, and 34% had 4 or more underlying medical conditions. Among all patients with an influenza-associated hospitalization who died, 48% of deaths occurred after hospital discharge; the median number of days from discharge to death was 9 (interquartile range, 3-19). Post-discharge deaths more often occurred in older patients and among those with underlying medical conditions. Only 37% of patients who died had "influenza" as a COD on their death certificate. Influenza was more frequently listed as a COD among persons who died in the hospital compared with cardiovascular disease among those who died after discharge.

conclusionsAll-cause mortality burden is substantial among patients hospitalized with influenza, with almost 50% of deaths occurring within 30 days after hospital discharge. Surveillance systems should consider capture of post-discharge outcomes to better characterize the impact of influenza on all-cause mortality.