A water marker monitored by satellites to predict seasonal endemic cholera

The ability to predict an occurrence of cholera, a water-related disease, offers a significant public health advantage. Satellite-based estimates of chlorophyll, a surrogate for plankton abundance, have been linked to cholera incidence. However, cholera bacteria can survive under a variety of coastal ecological conditions, thus constraining the predictive ability of the chlorophyll, since it provides only an estimate of greenness of seawater. Here, a new remote-sensing-based index is proposed: Satellite Water Marker (SWM), which estimates the condition of coastal water, based on observed variability in the difference between blue (412 nm) and green (555 nm) wavelengths that can be related to seasonal cholera incidence. The index is bounded between physically separable wavelengths for relatively clear (blue) and turbid (green) water. Using SWM, prediction of cholera with reasonable accuracy, at least two months in advance, can potentially be achieved in the endemic coastal regions.