Epidemiological characterization and seasonality of respiratory syncytial virus in the United Arab Emirates: A five-year study at a tertiary care hospital, 2018–2022

Background: Respiratory syncytial virus (RSV) is a major cause of morbidity and hospitalization in infants and young children. Understanding its epidemiological patterns is essential for guiding preventive strategies. This study examined the epidemiology and seasonality of RSV over a-five-year period - before and during the COVID-19 pandemic - at a tertiary hospital in the United Arab Emirates (UAE). Methods: Medical records of children ≤ 5 years tested for RSV at Tawam Hospital between January 2018 and December 2022 were reviewed. Duplicate samples within four weeks were excluded, with PCR prioritized over antigen results. Both RSV-A and RSV-B types were analyzed. Season onset was defined as two consecutive weeks with RSV positivity > 3 % (PCR) or > 10 % (antigen). The association between RSV type and both hospitalization and hospital length of stay was investigated. Data were analyzed by year, RSV type, month, and epidemiological week. Results: A total of 39,760 RSV tests (24,924 PCR; 14,836 antigen) were performed on 15,326 unique children. Testing increased over time, and the median age of screened children rose from 11 months (2018) to 15 months (2022). Overall RSV positivity was 11 % (2018), 11 % (2019), 2.9 % (2020), 16 % (2021), and 6.1 % (2022). RSV-A predominated in 2020–2021, while RSV-B was more common in 2022. RSV seasonality shifted during the pandemic, with delayed onset in 2020–2021, but returned to pre-pandemic timing in 2022. Of 2189 RSV-associated hospitalizations, 60.2 % occurred during 2021–2022. Infants < 6 months had the longest hospital stays (mean 5.8 days). Although RSV type was not associated with the length of hospital stay, infection with RSV-B was significantly associated with 6.7-times higher odds of hospitalization (aOR: 6.71; 95 % CI: 5.26–8.66; P < 0.001). Conclusion: The study underscores the impact of COVID-19 on RSV seasonality in the UAE and highlights the need for sustained surveillance to optimize RSV prevention strategies.