Surveillance of respiratory viruses in severe acute respiratory infections in Southern Brazil, 2023-2024.

Severe Acute Respiratory Infection (SARI) is one of the leading causes of death worldwide, representing a significant public health challenge. Respiratory viruses are the primary pathogens responsible for these infections, and their ability to evolve and spread efficiently contributes to their widespread circulation. Here, we examined the epidemiological characteristics of SARI cases reported over one year (February 2023 To February 2024) in Rio Grande do Sul, the southernmost state in Brazil. Additionally, 4,000 negative specimens for influenza, Respiratory Syncytial Virus (RSV), and SARS-CoV-2, tested routinely, were evaluated by an expanded PCR respiratory panel (11 pathogens). During the study period, 14,816 SARI cases were reported: 3,396 cases due to SARS-CoV-2 infection, 2,329 To RSV, 1,124 due to influenza (802 influenza A and 322 influenza B), and 7,803 due To undefined etiological agents. Differential diagnostics allowed for identifying at least one respiratory pathogen in 1,741 (43.5%) of the 4,000 SARI cases tested. Human rhinovirus was the most frequently detected virus (in 63.3% of positive cases), followed by metapneumovirus (17.7%), parainfluenza (15.9%), adenovirus (13.6%), and bocavirus (11.6%). Our findings highlight the significant role of a diverse range of respiratory viruses contributing to severe illness and mortality. Additionally, we observed ongoing shifts in the seasonal patterns of these viruses, underscoring the dynamic nature of respiratory virus circulation. These results emphasize the need for comprehensive interventions to mitigate the impact of respiratory infections and ensure an adequate public health response.