Temporal Patterns and Distribution of Laboratory-Confirmed Respiratory Pathogen Detections in a Tertiary Hospital in Southern Brazil (2023–2026)

Objective: To describe the epidemiological, clinical, and seasonal patterns of respiratory viral infections in Southern Brazil between January 2023 and April 2026. Methods: A retrospective observational descriptive study was conducted at a private hospital including laboratory-confirmed cases of SARS-CoV-2, influenza A (H3N2 and H1N1), respiratory syncytial virus (RSV A and B), rhinovirus, adenovirus, metapneumovirus, enterovirus, bocavirus, parainfluenza viruses, and seasonal coronaviruses. Respiratory pathogens were detected using molecular testing (XGEN MULTI PR24 FLOW CHIP) or rapid antigen detection tests. Demographic, clinical, and temporal data were analyzed according to age group. Results: A total of 18,214 detections were identified. Influenza A was the most frequent pathogen (48.08%), followed by SARS-CoV-2 (23.73%) and RSV A (8.65%). Hospitalization occurred in 20.44% of patients, 21.11% of hospitalized individuals required intensive care, and 2.93% required mechanical ventilation. Adults showed alternating seasonal peaks of influenza A and SARS-CoV-2, with influenza A predominating during colder seasons and SARS-CoV-2 during warmer periods. In children, SARS-CoV-2 incidence was lower, whereas RSV A and other respiratory viruses showed greater circulation. Declines in influenza A and COVID-19 detections were observed during periods that temporally overlapped with national vaccination campaigns; however, vaccination coverage was not assessed in this study. Conclusions: Respiratory viral infections remained frequent in the post-pandemic period, reinforcing the importance of continuous surveillance, seasonal monitoring, and vaccination strategies.