A Global Analysis of the Effects of Hydrometeorological Variables on Human Leptospirosis Incidence

Leptospirosis is a water-related zoonosis with a global distribution. Peaks in incidence in humans have often followed heavy rainfall or flooding, because of increased vulnerability and exposure to infected water, in addition to pre-existing socio-economic conditions. Greater runoff itself may increase the concentration of leptospira, the etiological agents, through release from soils where they survived after being shedded by a carrier, according to a hypothesis which has been growing in popularity. We investigate the role of different hydrometeorological parameters and their extremes on the risk of leptospirosis for different outbreaks over time and geography: rainfall, runoff, temperature and soil moisture. We study how local context modulates these effects, where present, in terms of properties such as urban character, prevalence of leptospirosis in rodents, and soil type. Our findings highlight the importance of hydrological modelling for a quantification of leptospirosis risk, and indicate how a changing climate may influence that risk.