Distinct pathways, shared risk factors: Leptospirosis and chikungunya at community and city scales in Salvador, Brazil.

Leptospirosis and chikungunya are poverty-related diseases influenced by climatic and socioenvironmental conditions. We investigated their distribution pattern in Salvador, Brazil, using serological data from four low-income communities and reported cases at the city level. At the community scale, lower household income, male gender, and proximity to open sewage were included as important predictors for both infections based on model performance. Leptospira infection was further associated with older age and lower land surface temperature, while chikungunya was linked to garbage collection services and lower flood risk. At the city scale, both diseases were best predicted by lower income, higher land surface temperature, lower population density, and a higher proportion of house-type dwellings. Leptospirosis risk was also linked to lower literacy and vegetation cover: chikungunya to vegetation patch density. These results highlight the importance of income, infrastructure, and environmental features, and support the potential role of green spaces in urban disease prevention.