The epidemiologic trend of respiratory syncytial virus has returned strongly to its origin after the pandemic: Five-year data from a single center.

Objective: Only a few studies have investigated the frequency and severity of respiratory syncytial virus (RSV) infections after the end of the pandemic regulations. This study aims to investigate the frequency and severity of RSV infections before, during, and after the pandemic in Turkey.
Materials and Methods: Patients under 18 years of age and those who tested positive for RSV between April 2018 and March 2023 were retrospectively reviewed. All patients were divided into three groups (pre-COVID-19, COVID-19, and post-COVID-19) according to admission date. Among inpatients, data were compared between the three groups to determine the impact of the pandemic on RSV epidemiology and clinical outcomes.
Results: A total of 9567 patients were tested for RSV, of which 1073 (11.2%) were positive and included in the study. Hospitalization occurred in 447 (41.7%) patients. Inpatients were younger than outpatients (p < .000). Among the three inpatient pandemic groups, clinical outcomes were statistically significantly worse in the post-COVID-19 group than in the other two groups. SpO ₂ was lower (p < .000), inhaled salbutamol requirement was higher (p < .000), length of stay was longer (p = .031), and ICU admission was higher (p = .023).
Conclusion: Although the RSV trend changed within 2 years after the COVID-19 outbreak, it returned to its usual seasonality last year. After the repeal of all COVID-19 measures and the normal life began, the number of RSV-positive patients and RSV-related hospitalizations increased, and the clinical outcomes of RSV worsened. This may be a result of decreased herd immunity due to a change in society's attitude toward epidemic diseases.
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