Large increase in mortality and hospital admissions among young children and the aged due to Influenza and Respiratory Syncytial Virus in Brazil in 2025

<jats:p>Background: Mortality and hospital admissions due to Severe Acute Respiratory Infection (SARI) peaked between January and August 2025 in Brazil. Methods: The Brazilian Ministry of Health data on hospital admissions and deaths caused by SARI were compiled by age group (&lt;5, 5-14, 15-49, 50-64, 65+ years) and quarter between January 2023 and June 2025. SARI causes were aggregated into SARS-Cov-2, Influenza, Respiratory Syncytial Virus (RSV), and other viruses (parainfluenza, adenovirus, rhinovirus, bocavirus, metapneumovirus). Multinomial regression was used to impute likely causes of death when these were not laboratory confirmed. Results: In the second quarter of 2025 (2025/2), RSV mortality rate among children &lt;5 years reached 60 per 100,000, which is a 43% increase compared with 2024/2. Mortality rate for the joint impact of parainfluenza, adenovirus, rhinovirus, bocavirus, and metapneumovirus in the same age group doubled from 20 to 40 on the same scale in 2025/2 compared to 2024/2. Over the same period, influenza mortality tripled among the aged, whereas mortality due to other respiratory viruses increased less dramatically, except for SARS-CoV-2, which decreased among the aged from 150 to 25 per 100,000 between 2023/1 and 2025/2. Other age groups remained relatively stable over the period. The variation in hospital admissions largely followed that of mortality. Conclusions: While deaths and hospital admissions caused by SARS-CoV-2 declined rapidly since 2023, mortality rates of other respiratory viruses, mainly influenza and RSV, increased significantly among children &lt;5 years and the aged in 2025/2. Public health policies that facilitate vaccine uptake against these infections should be given high priority.</jats:p>