Leptospirosis, an infectious disease caused by bacteria of the genus Leptospira, is mainly transmitted through contact with water contaminated by animal urine and becomes particularly concerning in urban contexts after floods. In recent years, Southern Brazil has experienced frequent extreme climate events. In 2024, Rio Grande do Sul (RS) faced one of the largest floods in its history, impacting public health. Suspicion of increased leptospirosis cases after this episode motivated a detailed analysis comparing disease patterns across states in the region. This study aimed to understand the impact of the flood on the epidemiological behavior of leptospirosis in RS compared with Santa Catarina (SC) and Paraná (PR), emphasizing the importance of future surveillance and rapid response actions in similar situations. Ecological study of reported leptospirosis cases in Southern Brazil in the first half of 2022 to 2024. Data were collected from SINAN using the following specifications: Notifiable Diseases – 2007 onwards (SINAN), Leptospirosis, State (RS, SC, PR), Year of notification (2022 to 2024), and reported cases. Data were then analyzed focusing on the impact of climatic events such as the RS flood. In the first half of 2022, 458 leptospirosis cases were recorded in Southern Brazil, with 186 in RS, 172 in PR, and 100 in SC. In 2023 (January–June), 569 cases were distributed as 234 in PR, 154 in SC, and 181 in RS. In 2024, cases rose to 927 across the region: 239 in PR, 138 in SC, and 550 in RS. In PR and SC, increases occurred mainly between 2022 and 2023, possibly explained by heavy rainfall in the region at that time. The most striking finding was the significant increase in leptospirosis cases in RS in 2024, especially in May, coinciding with the major flood ‒ 550 cases in the first half of 2024 compared with 181 in 2023. Thus, reported cases are closely related to rainfall and flooding patterns, which is alarming given the increasing occurrence of extreme climate events.
Amaral et al. (2026) studied this question.