Respiratory syncytial virus disease burden in adults aged ≥50 years old: A retrospective national surveillance database analysis in Mexico (2015-2023).

Despite widespread circulation among older adults and those with comorbidities, the burden of respiratory syncytial virus (RSV) in this population remains under-recognized. This study characterized the epidemiology of RSV among adults aged ≥50 years in Mexico. We retrospectively analyzed data from the National Epidemiological Surveillance System (SiNaVE) in Mexico, including laboratory-confirmed RSV cases between 01/01/2015 and 31/12/2023. Descriptive analyses characterized RSV occurrence, age, symptoms, comorbidities, and temporal patterns. Temporal and spatial autocorrelation analyses assessed RSV circulation. Spatial regression models examined associations between structural health determinants and the geographic distribution of RSV cases. We identified 7,958 RSV cases of all ages, of which 9.4% occurred in adults aged ≥50 years. Among these, 60.5% were female patients, and 53.8% had more than one comorbidity, the most common being hypertension and diabetes. Fatality rate was 12.6% among adults aged ≥50 years. RSV positivity was higher among the older age groups and fluctuated over the years, peaking in 2019 and declining in 2020. RSV seasonality was observed, with the highest frequency in October, and broader peaks than those of influenza. Spatial analysis revealed heterogeneous RSV activity across Mexico, with Ciudad de Mexico and Mexico accounting for ~36% of cases. Socioeconomic disadvantage was associated with fewer reported RSV cases. RSV represents a substantial and likely under-recognized burden among Mexican adults. The seasonality and spatial heterogeneity highlight the need for active, timely, and adult-focused RSV surveillance to improve awareness, equitable detection, and targeted prevention strategies, including vaccination.