Impact of the 2024 Floods on the Increase in Leptospirosis Cases in the City of Canoas, Southern Brazil: A Comparison with 2023

Introduction: Leptospirosis, a zoonosis caused by Leptospira bacteria, is transmitted through contact with infected animals’ urine, often in flooded, unsanitary environments. In 2024, Rio Grande do Sul experienced severe floods due to heavy rains, inundating cities like Canoas and creating ideal conditions for leptospirosis spread through contaminated water exposure.

Methods: Data on confirmed leptospirosis cases in Canoas for 2023 and 2024 were sourced from the Department of Informatics of the Unified Health System (DATASUS). Monthly notifications were analyzed using time-series analysis to detect trends and descriptive statistics to highlight peak incidence periods. Historical data from 2020–2022 were reviewed to place recent findings in a multi-year context.

Results: In 2023, 14 cases were recorded, while 27 cases were reported in the first half of 2024. From March to June, aligned with the 2024 flooding, cases increased from 7 in 2023 to 27 in 2024, with May 2024 representing 52% of the year’s total. Historical data (2020–2022) show an annual average of 12 to 15 cases, suggesting the 2024 surge exceeds typical fluctuations, particularly during flood-affected months. This indicates a significant deviation linked to environmental conditions.

Conclusions: The 2024 floods in Rio Grande do Sul likely contributed to the notable rise in leptospirosis cases in Canoas, as floodwaters heightened infection risk. Compared to historical averages, this increase appears anomalous, reinforcing the influence of extreme weather on disease incidence. These findings emphasize the importance of tailored public health responses in flood-prone regions, such as improved sanitation and early warning systems, to mitigate future outbreaks and protect vulnerable populations.