Analysis of Respiratory Syncytial Virus cases at Hospital Clínico San Carlos in Madrid during 2018-2025.

Abstract

Respiratory syncytial virus (RSV) infection is one of the main causes of morbidity and mortality in infants under 6 months of age; however, it can cause respiratory infection at other stages of life. In the period 2018-2025, the number of cases has risen considerably, with positivity mainly concentrated in children under 24 months of age. The SARS-CoV2 pandemic caused modifications in affected population groups and seasonality. The percentage of RSV in children under 6 months of age in the period 2024-2025 was significantly lower than in the 2023-2024 season. In contrast, in the elderly population, especially those over 86 years of age, the percentage of positive cases has increased significantly. From 2022 onwards, the incidence of virus positivity shows a more stable and sustained pattern from October to April compared to previous years. The aim of this review is to assess the evolution of the type of patient diagnosed with RSV infection and to determine early whether the beginning of the vaccination campaign has reduced the incidence in the susceptible population. The availability of epidemiological information to guide decision-making is of great importance for evaluating the effectiveness of these measures and adopting changes in the use of vaccination in the general population.