Clinical Phenotypes and Outcomes Associated With Respiratory Syncytial Virus Infection in Critically Ill Patients: A Retrospective Multicenter Cohort Study in Greater Paris Area Hospitals, 2017–2023

Abstract Background Respiratory syncytial virus (RSV) is one of the deadliest respiratory viruses. There is a need to better identify prognostic factors in RSV-infected patients, particularly those requiring intensive care unit (ICU) admission, with a focus on immunosuppressed patients. Methods This was a multicenter, retrospective cohort study of RSV-infected adults hospitalized in 17 ICUs in the Greater Paris area between 1 August 2017 and 1 May 2023. The primary endpoint was all-cause day 30 mortality. Supervised and unsupervised analyses were performed. Results During the study, 474 RSV-infected patients were admitted (56% male, mean age 65±17 years, 34% immunosuppressed). Day 30 mortality was 14%. Immunosuppression was linked to mortality (aOR=2.10, 95% CI [1.14;3.80], p=0.035). Cluster analysis identified three groups: (1) immunosuppressed (17%, highest mortality 21%), (2) older with comorbidities (43%, mortality 14%), and (3) younger (37%, lowest mortality 9%). Conclusions One-third of ICU patients with RSV infection were immunosuppressed, and both supervised and unsupervised methods linked immunosuppression to day 30 mortality. Anti-RSV therapies preventing ICU admission should be evaluated in this subgroup.