Climate Variability and Cholera Risk in Equatorial Africa

Cholera is a water-borne, ecologically mediated disease. For this reason there is both expectation and evidence that environmental variability, particularly hydroclimatic extremes, plays a significant role in modifying the risk of outbreaks and amplifying cholera transmission in endemic areas. At the same time, cholera risk is fundamentally intertwined with human behavior and infrastructure. While Vibrio cholerae is endemic to many coastal and brackish inland water bodies, transmission of pandemic V. cholerae O1 within human populations depends on behavior-related exposure to contaminated water, can involve imported risk associated with human travel, and, for sustained outbreaks, almost always depends on an absence of effective sanitation facilities. This complexity poses a challenge for environmentally-informed cholera warning systems, as it does for environmentally-informed warnings for many human-mediated infectious diseases. In the case of cholera, one result is that risk can be exacerbated by different types of climate extremes in different regions: in a place where preferred drinking water sources dry up in drought, for example, dry conditions can enhance risk, while in a place where flooding leads to contamination of previously safe water or increased contact with cholera-containing water, high rainfall conditions can be a primary risk factor. Here, we present work on environmentally-informed cholera risk warning in equatorial Africa, with a focus on the Democratic Republic of Congo for the period 2000-present. We emphasize the challenges and opportunities of combining Earth Observations with large historical cholera datasets, and investigate strength and mechanism of association between climate extremes and cholera outbreaks in this period.