Contemporary respiratory syncytial virus epidemiology, outcomes and practice variation after haematopoietic cell transplantation: A multicontinental cohort study

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Background Respiratory syncytial virus (RSV) is an important cause of respiratory morbidity in haematopoietic cell transplant (HCT) recipients, yet comparative data across different healthcare settings remain limited. We aimed to evaluate contemporary RSV burden, real-world management variation, and clinical outcomes across three HCT centres in South Africa and the Netherlands. Methods This retrospective multicentre cohort included adults (≥18 years) with PCR-confirmed RSV infection in the HCT care pathway between January 2015 and December 2024. Observed RSV case burden was expressed as the proportion of all transplants and as detected cases per 100 person-years. RSV testing was clinician-driven rather than protocolised, and the number of transplant recipients tested for RSV was not uniformly available across centres. Results Among transplant populations comprising 1,189 HCTs, 82 PCR-confirmed RSV infections were identified (65 EMC; 9 SG; 8 WDG). Observed centre-level case proportions ranged from 4.2% to 7.7%, corresponding to 1.2-1.5 detected cases per 100 person-years. Most infections (65%) occurred within 15 months of HCT, with 43% occurring between 0 and 9 months. Respiratory viral co-infections were documented in 16-33% of cases. Hospitalisation, ICU admission, and in-hospital mortality ranged from 25-56%, 3-22%, and 3-13%, respectively. Ribavirin-based treatment was used only at EMC. Conclusion PCR-confirmed RSV infection represented a clinically relevant but modest observed case burden in these HCT populations and was associated with generally favourable short-term outcomes. Most infections occurred early after HCT, suggesting a clinically relevant period of increased vulnerability. Because testing was clinician-driven and testing denominators were unavailable, direct comparisons of incidence between centres require caution.