Respiratory syncytial virus (RSV) in older adults: from infection to outcomes - who gets sick, who gets hospitalized, who survives?

Respiratory syncytial virus (RSV) is a virus responsible for acute respiratory infections and is widely recognized as a major pathogen in the paediatric population. Thus, the burden of RSV in the adult population remains poorly understood, as epidemiological studies mainly rely on PMSI (Medicalization of Information Systems Program) data, which are coded for economic purposes, and because many adults RSV infections remain underdiagnosed. The aim of this study was to describe epidemiological and clinical characteristics of RSV infections in elderly population across four university hospitals in north-western France during the 2022-2023 epidemic season. This retrospective cohort included all patients aged 60 years and older who tested positive for RSV between September 1st, 2022, and January 31st, 2023, in four university hospitals. Viral detection was performed using molecular assays on respiratory samples. Clinical, demographic, biological, and coding data were collected from medical records and hospital information systems. Outcomes included need for oxygen therapy, intensive care admission, in-hospital mortality, length of stay, readmission within 90 days for a respiratory or cardiac reason, and changes in living arrangements. Statistical analyses used descriptive methods and standard tests for comparisons. A total of 647 patients were included. The mean age was 77.8 years, and most patients had at least one chronic medical condition, primarily respiratory or cardiac. 508 (78.5%) patients were hospitalized. The mean hospital stay was 16.2 days, and oxygen therapy was required in 68.3% of cases. In-hospital mortality reached 11.0%. Among survivors, 38.0% were readmitted within 90 days for a respiratory or cardiac reason. A notable proportion of patients experienced a loss of autonomy leading to institutional placement at discharge. RSV was coded in the PMSI database as a diagnosis in approximately two-thirds of hospitalizations, with substantial variations between centers. RSV infection in older adults was associated with significant morbidity, prolonged hospitalization, and a frequent decline in functional status. The study also identified heterogeneity in coding practices and emphasized limitations of PMSI data for capturing respiratory syncytial virus burden. These findings support the need for expanded screening, along with targeted preventive strategies and structured post-discharge follow-up to reduce the long-term burden of RSV in older populations.