Spatiotemporal dynamics of leptospirosis in Europe: a retrospective observational study with prospective projections

Background: spp., with a substantial burden on both human and animal health. Transmission occurs through contact with the urine of infected animals, with rodents serving as the main disease reservoir. Climate and environmental changes, including higher temperatures, heavy rainfall, urbanization, forest encroachment, and biodiversity loss are expected to alter rodent populations and disease dynamics, raising concerns about the increasing risk of leptospirosis in Europe. Despite this, no comprehensive risk map or modelling study has been conducted at the European scale. Given this, we aimed to quantify spatiotemporal patterns of leptospirosis risk in Europe and project future incidence rate under climate change scenarios. Methods: In this study, we present a Europe-wide spatiotemporal assessment of leptospirosis risk, integrating epidemiological, environmental and climate data. Using monthly leptospirosis cases from the European Surveillance System (TESSy) between 2010 and 2023, we developed a Bayesian hierarchical model to identify key risk factors, including the 3-month Standardised Precipitation Evapotranspiration Index (SPEI-3), mean temperature (Tmean), forest human nexus and mammal richness. Future changes in disease incidence rate were also investigated under two climate/socio-economic scenarios, namely the Shared Socioeconomic Pathways (SSP) 4.5 and 8.5. Findings: Over the 2010-2023 period, leptospirosis risk was higher in areas with elevated SPEI-3 (maximum relative risk [RR] = 1.62; 95% CrI: 1.20-2.10) and higher Tmean values (maximum RR = 5.28; 95% CrI: 2.65-11.12), both with a 1-month lag. Leptospirosis incidence rates were greater in warm coastal regions and densely populated areas. We observed a complex relationship between disease risk and the forest human nexus (maximum RR = 1.23; 95% CrI: 0.96-1.55), and a negative association with mammal species richness (minimum RR = 0.63; 95% CrI: 0.40-0.98), suggesting a potential dilution effect. Finally, under future climate scenarios, we found that leptospirosis incidence rate is projected to increase, particularly under high greenhouse gas (GHG) emissions, with larger rises expected in the long-term period (2081-2100) than in the short-term period (2041-2060). Interpretation: Climate and environmental factors can elevate the risk of leptospirosis with climate change projected to have a significant impact on future risk levels. Our findings underscore the need for proactive measures to mitigate the effects of climate-sensitive zoonoses, such as leptospirosis, across Europe. Integrating spatial and temporal disease models into early warning systems, alongside environmental management and climate mitigation strategies, can support timely interventions and enhance public health resilience. Funding: This research received no specific grant from any funding agency in the public, private, or not-for-profit sectors.