Burden and Characteristics of RSV-Associated Hospitalizations in Switzerland: A Nationwide Analysis from 2017 to 2023.

Respiratory syncytial virus (RSV) is a major cause of respiratory illness, particularly in children, yet its burden in adults-especially in older adults-remains under-recognized. We analyzed RSV-related hospitalizations in Switzerland from 2017 to 2023 using national data from the Federal Statistical Office, including cases with RSV coded as either a primary or secondary diagnosis. Over 35,000 RSV-related hospitalizations were recorded. The highest incidence occurred in children under 10 years (390 per 100,000/year), with a second peak in adults ≥ 80 years (151 per 100,000/year). Older adults (≥60 years) accounted for more than 9700 hospitalizations overall, with an average of over 16,600 total hospital days per year. Average length of stay (LOS) was shortest in young children (4.6 days) and highest in adolescents (13.9 days), while in adults, it increased from 6.8 days (age 20-29) to 12.3 (age ≥ 80). Mechanical ventilation rates peaked at 12.6% in 60-69 year olds, and in-hospital mortality at 7.1% in those ≥80 years. In adults, RSV was more often recorded as a secondary diagnosis and commonly associated with chronic comorbidities, including chronic obstructive pulmonary disease, heart failure, kidney disease, and diabetes. Frailty-related diagnoses-such as cognitive or motor impairment, delirium, and need for nursing care-were also frequent. These findings highlight the importance of improved adult RSV surveillance and targeted prevention strategies in high-risk populations.