Global Health in Times of Climate Crisis: Leptospirosis Mortality in Rio Grande Do Sul After the 2024 Floods

Leptospirosis is a bacterial zoonosis transmitted through exposure to water contaminated with the urine of infected animals, especially rodents. Flooding situations increase population exposure to unhealthy environments, favoring disease dissemination. In April 2024, the state of Rio Grande do Sul experienced the largest extreme climate event in its history, with cumulative rainfall exceeding 700 mm in some regions. This study aimed to evaluate the impact of the 2024 floods on leptospirosis mortality in the state, comparing post-flood data with the same period in 2023. This was an observational, retrospective, ecological study with a before-and-after design. Aggregated data on confirmed cases and deaths from leptospirosis reported in the Notifiable Diseases Information System (SINAN) were used, covering April to August of 2023 and 2024. Mortality rates were calculated per 100,000 inhabitants, based on the number of deaths and IBGE population estimates for 2023 and 2024. In 2023, 477 confirmed cases of leptospirosis and 25 deaths were recorded, corresponding to a mortality rate of 0.23 per 100,000 inhabitants. In the same period of 2024, 823 cases and 55 deaths were reported, with a rate of 0.49 per 100,000 inhabitants ‒ more than double that of the previous year. In 2024, 75% of deaths occurred among men, predominantly in the 40–59-year age group. Most deaths were concentrated in the metropolitan region, with a peak of notifications in June. The marked increase in incidence and mortality rates in 2024 suggests a direct impact of flooding on disease epidemiology and highlights the vulnerability of urban populations exposed to climate disasters. The findings reinforce the importance of preventive strategies, strengthening epidemiological surveillance, and developing rapid responses in environmental emergency scenarios.