Respiratory Syncytial Virus vs Influenza Virus Infection: Mortality and Morbidity Comparison Over 7 Epidemic Seasons in an Elderly Population

Background: Respiratory syncytial virus (RSV) infection is gaining interest due to the recent development of vaccines but is still misdiagnosed in the elderly. The primary objective was to compare all-cause mortality at day 30. Secondary objectives were to compare clinical presentation and rates of consolidative pneumonia, hospitalization, and intensive care unit (ICU) admission. Methods: A single-center retrospective study was conducted in a French university hospital during 7 epidemic seasons including 558 patients aged ≥75 years: 125 with RSV and 433 with influenza (median age, 84.8 years). Results: Patients with RSV had more respiratory symptoms (wheezing, dyspnea) whereas patients with influenza had more general symptoms (fever, asthenia, myalgia). The following were higher in the RSV group: consolidative pneumonia (28.8% vs 17.2%, P =. 004), hospitalization (83.2% vs 70%, P =. 003), ICU admission (7.2% vs 3.0%, P =. 034), and length of stay (median [IQR], 9 days [2-16] vs 5 days [0-12]; P =. 002). Mortality rates at day 30 were comparable (9.6% vs 9.7%, P =. 973). Conclusions: This study included the largest cohort of patients infected with RSV aged >75 years documented in-depth thus far. RSV shares a comparable mortality rate with influenza but is associated with higher rates of consolidative pneumonia, hospitalization, ICU admissions, and extended hospital stays.