Geospatial patterns of cholera seasonality and their association with climate in sub-Saharan Africa

Cholera is a waterborne disease that causes between 1 and 4 million cases per year, with 87 million people living in areas with high incidence (> 1 case per 1000 people per year) in sub-Saharan Africa (SSA). Few studies have focused on the seasonal occurrence of cholera and its link to hydro-climatic drivers in SSA, most of which were limited to specific regions. Knowledge on seasonal patterns and their associations with climatology may support the 2030 roadmap for cholera control and elimination. We here analyze an extensive cholera dataset covering multiple spatial scales from international organizations, ministries of health and published literature. We use a Bayesian statistical framework to systematically quantify the seasonality of cholera occurrence in all countries in SSA at monthly temporal resolution and at the first and second administrative levels. We then perform an exploratory analysis of the association between inferred seasonality for cholera incidence data inventoried at the scale of the administrative unit, relevant gridded and administrative unit human systems covariates, and gridded Earth Observations of meteorology and surface hydrology, climatologically averaged and aggregated to the scale of cholera case data. We find statistical support for seasonal variations in cholera occurrence in most countries in SSA (32/40), with support for sub-national differences in seasonality in half of the countries (16/32). The strength of seasonality varied strongly both between and within countries. We found support for the association between seasonality and climatology, with different levels of variance explained depending on sub-regions. These results highlight the association between seasonality and cholera occurrence across countries in SSA. Identified associations between seasonality and climatology motivate further exploration of regionally-specific mechanisms linking hydro-climatic drivers and the occurrence of cholera, possibly informing the development of early warning systems in specific settings.