Population Vulnerability to Biannual Cholera Outbreaks and Associated Macro-Scale Drivers in the Bengal Delta

Abstract

Abstract. The highly populated floodplains of the Bengal Delta have a long history of endemic and epidemic cholera outbreaks, both coastal and inland. Previous studies have not addressed the spatio-temporal dynamics of population vulnerability related to the influence of underlying large-scale processes. We analyzed spatial and temporal variability of cholera incidence across six surveillance sites in the Bengal Delta and their association with regional hydroclimatic and environmental drivers. More specifically, we use salinity and flood inundation modeling across the vulnerable districts of Bangladesh to test earlier proposed hypotheses on the role of these environmental variables. Our results show strong influence of seasonal and interannual variability in estuarine salinity on spring outbreaks and inland flooding on fall outbreaks. A large segment of the population in the Bengal Delta floodplains remain vulnerable to these biannual cholera transmission mechanisms that provide ecologic and environmental conditions for outbreaks over large geographic regions.

A new methodology for modelling of health risk from urban flooding exemplified by cholera – case Dhaka, Bangladesh

“…The fall peak in the Bengal Delta was found to be correlated with high flow in the Ganges-Brahmaputra-Meghna basin and with the flooding Extent , and large outbreaks in Dhaka have shown to be correlated with the floods of , 2004(Schwartz et al, 2006 and 2007 (Hashizume et al, 2008;Alam et al, 2011). The studies by Akanda et al (2013), however, do not directly represent a causal connection but identify two plausible physical variables in the transmission process.…”

“…Dhaka also experiences biannual outbreaks. The spring peak can be explained by intrusion of salt water into the Bengal Delta which, combined with high temperatures, gives favourable conditions for V. cholerae and subsequently an increased risk of infection (Akanda et al ., , , ). A similar situation was observed in the Indus river basin where cholera risk is correlated to above average temperatures followed by above average rain (Jutla et al ., ).…”

“…A similar situation was observed in the Indus river basin where cholera risk is correlated to above average temperatures followed by above average rain (Jutla et al ., ). The fall peak in the Bengal Delta was found to be correlated with high flow in the Ganges–Brahmaputra–Meghna basin and with the flooding Extent (Akanda et al ., ), and large outbreaks in Dhaka have shown to be correlated with the floods of 1988, 1998, 2004 (Schwartz et al ., ) and 2007 (Hashizume et al ., ; Alam et al ., ). The studies by Akanda et al .…”

“…The studies by Akanda et al . (), however, do not directly represent a causal connection but identify two plausible physical variables in the transmission process.…”

Predictive Time Series Analysis Linking Bengal Cholera with Terrestrial Water Storage Measured from Gravity Recovery and Climate Experiment Sensors

“…In contrast, high river flow after heavy rains inundates large terrestrial landscapes, creating conditions favorable for cholera with cross-contamination, and the resulting mixing of bacterialaden water spread over vast spatial scales. [1][2][3][5][6][7][8][9][10][11] Growth of Vibrio cholerae, the causative agent for the disease, in riverine, estuarine, and coastal waters has been shown to be strongly linked to a set of biological parameters namely nutrients in water, temperature, pH, salinity, plankton, and zooplankton 4,12 that are further associated with large-scale climatic processes. 13,14 Because cholera bacteria are autochthonous to the aquatic environment and eradication of the pathogen is not possible, forecasting conditions favorable for growth of the cholera bacteria in the environment is achievable if relevant environmental conditions can be linked to large-scale geophysical phenomena.…”