Comparison of 28-Day Mortality Between Hospital- and Community-Acquired Influenza Patients

This study aimed to compare 28-day mortality between patients have hospital-acquired influenza (HAI) and those have community-acquired influenza (CAI) during the 2017-2019 influenza seasons in a tertiary care center in İstanbul, Türkiye.

This retrospective cohort included all hospitalized patients who had confirmed influenza infection and were over 17 years old. HAI was defined as a case of influenza that tested negative in a PCR test or had no signs of influenza on admission but with a positive test result at any point after 72 hours of admission. CAI was defined as a case of influenza diagnosed within 72 hours of admission or before admission. The primary outcome was 28-day mortality after diagnosis. Biological sex, admission to the intensive care unit (ICU), presence of chronic obstructive pulmonary disease, cardiovascular and immunosuppressive comorbidities, influenza subtype, and other variables identified with univariate analyses (p<0.25) were entered into logistic regression analysis.

During the study period, 92 (46%) of 201 hospitalized patients who tested positive for influenza were identified as HAI, and the rest (109) were identified as CAI. Univariate analysis showed no differences between survivors and non-survivors in patient characteristics, except non-survivors were more likely to have an ICU admission. The multivariable logistic regression analysis results showed that HAI was associated with 5.6-fold increased odds of mortality (95% confidence interval [CI]=1.6-19.3; p=0.006), after adjustment for age, gender, comorbidity, and ICU admission.

The results of this study revealed that patients who had HAI were more likely to die within 28 days compared to those who had CAI after controlling for key confounders. The high rate of HAI underscores the critical importance of robust infection control measures for hospital-acquired viral infections. Additional research and targeted interventions are necessary to improve the HAI prognosis.