Respiratory Syncytial Virus-Associated Severe Acute Respiratory Infections in Hospitalized Patients at a University Hospital Center in Rabat, Morocco: An Epidemiological Overview

Respiratory syncytial virus (RSV) imposes a substantial burden of severe acute respiratory infection (SARI), especially in young children and the elderly. Methods: We describe RSV epidemiology among hospitalized SARI patients at the Ibn Sina University Hospital Center (Rabat, Morocco) from 1 January 2021, to 31 December 2025, using multiplex PCR (BioFire® RP2.1plus or Xpert® SARS-CoV-2/Flu/RSV). Results: Among 4604SARI samples, RSV prevalence was 16.1% (739/4604), predominantly pediatric (88.6%, p < 0.001), with peak burden in infants <6 months (70.4% of cases, p < 0.001). Pediatric prevalence was 28.3% (655/2316) vs. 3.8% (84/2204) in adults (p < 0.001), with predominance in the elderly ≥60 years (51/1041, 4.9%). Co-infections occurred in 46.7% (310/665) of FilmArray-tested positives (total = 665), led by rhinovirus/enterovirus (198/310, 63.9%), and were significantly higher in children (48.5%, p < 0.001). RSV peaked in winter (51.6%), except for summer dominance in 2021 (52.5%), reflecting COVID-19 non-pharmaceutical intervention effects. Conclusions: These data establish Morocco’s first comprehensive RSV surveillance baseline, highlighting post-pandemic epidemiological shifts. As maternal vaccines and monoclonal antibodies emerge, these data inform optimal implementation in low- and middle-income countries (LMICs).