Outcomes of SARS-CoV-2 and Seasonal Viruses Among 2 Million Adults Hospitalized for Severe Acute Respiratory Infection During the COVID-19 Pandemic in Brazil.

Background: The outbreak of the COVID-19 pandemic has had a profound impact on the circulation of seasonal respiratory viruses. This study aimed to compare the outcomes of SARS-CoV-2 and seasonal viruses in adults hospitalized with severe acute respiratory infection during the COVID-19 pandemic.

Methods: This population-based cohort study included patients aged >18 years hospitalized for severe acute respiratory infection in Brazil between February 2020 and February 2023. The primary outcome was in-hospital mortality. A competing risk analysis was used to account for competing events.

Results: In total, 2 159 171 patients were included in the study. SARS-CoV-2 was the predominant virus (98.7%). Among patients testing positive, the cumulative incidence of in-hospital mortality was 33.1% for SARS-CoV-2, 31.5% for adenovirus, 21.0% for respiratory syncytial virus, 18.7% for influenza, and 18.6% for other viruses. SARS-CoV-2 accounted for 99.3% of the deaths. Older age, male sex, comorbidities, hospitalization in the northern region, and oxygen saturation <95% were the common risk factors for death among all viruses.

Conclusions: In this large cohort study, individuals infected with SARS-CoV-2 or adenovirus had the highest risk of mortality. Irrespective of the virus type, older age, male sex, comorbidities, hospitalization in vulnerable regions, and low oxygen saturation were associated with an increased risk of fatality.