Epidemiological and Environmental Risk Factors for Human Leptospirosis Cases in Buenos Aires Province, Argentina (2000-2016): An Ecological Study.

INTRODUCTION

Leptospirosis is a globally significant zoonotic disease particularly prevalent in subtropical regions subject to recurrent flooding. In Argentina, Buenos Aires province ranks third nationally in confirmed human cases. This study characterises the epidemiology of human leptospirosis in Buenos Aires province and assesses the association between rainfall, Terrestrial Water Storage (TWS), and leptospirosis cases.

METHODS

An ecological time-series study was conducted using leptospirosis notifications from 85 municipalities between 2000 and 2016. Cases were confirmed by microscopic agglutination test (MAT). Rainfall data were obtained from 30 meteorological stations, while TWS was derived from GRACE satellite data.

RESULTS

Of 5629 suspected cases, 487 (8.7%) were confirmed, with Canicola identified as the main infecting serogroup. The case fatality rate was 2.3%. Middle-aged males (79.3%) were most affected, with exposure linked to contaminated water and domestic animals. Thirty-one outbreaks occurred during the study period, resulting in a 32% increase in confirmed cases. Leptospirosis exhibited an interannual pattern associated with excess water, with cases rising significantly when rainfall exceeded the annual average. Leptospirosis incidence was highly correlated with TWS variations (R = 0.82, p = 0.00019), whereas annual precipitation showed a weaker, non-significant correlation (R = 0.37, p = 0.176).

CONCLUSIONS

Unlike precipitation, TWS integrates soil moisture and shallow waterlogging conditions that favour leptospiral survival and transmission in Buenos Aires province. Given the ecological design, results reflect population level associations and should be interpreted as preliminary ecological evidence, acknowledging potential residual confounding from socioeconomic, occupational, and sanitation factors. TWS derived from GRACE offers a complementary metric to precipitation for hydrological risk monitoring and could be incorporated into early warning systems and public health policy to reduce leptospirosis burden in the most vulnerable municipalities.