Clinical characterization of patients and genomic description of respiratory syncytial virus in adults and paediatric patients in a northeastern Mexican population

Introduction. Respiratory syncytial virus (RSV) is a frequent cause of lower respiratory tract infections among children under 2 years old and adults over 60. Compared to other causes of viral pneumonia in adults, it is associated with a higher risk of intensive care unit admission, mechanical ventilation and 30-day mortality. Hypothesis/Gap Statement. Despite the global recognition of RSV as a cause of respiratory disease, the epidemiological information available on its distribution in Mexico and Latin America among adults is limited. Aim. To characterize the epidemiological, clinical and molecular features of RSV infections in the Mexican population during the 2023–2024 winter season. Methodology. An observational, retrospective and descriptive study was conducted including patients of all ages with RSV detected by reverse transcriptase/real-time PCR during the 2023–2024 winter season. Results. In our study, 50% of adults and 96% of paediatric patients with RSV were admitted for at least 24 h. The most frequent comorbidities in adults were systemic hypertension and diabetes. Approximately one-third of adults were over 65 years of age, and the overall in-hospital mortality in the adult group was 24%, in contrast to 6% in-hospital mortality in the paediatric population. Genomic analysis identified RSV serotype A as predominant. Complete genome sequencing revealed circulation of the A.D.1 clade, consistent with lineages from the southern USA, marking the first complete sequencing of RSV isolates from Mexican patients. Conclusion. RSV represents a significant cause of respiratory infection in Mexico across age groups, with substantial mortality in adults. The identification of the A.D.1 clade underscores the importance of continuous epidemiological and molecular surveillance for understanding RSV circulation patterns in the region.