Hydrometeorology and flood pulse dynamics drive diarrheal disease outbreaks and increase vulnerability to climate change in surface-water-dependent populations: A retrospective analysis

Abstract

BackgroundThe impacts of climate change on surface water, waterborne disease, and human health remain a growing area of concern, particularly in Africa, where diarrheal disease is one of the most important health threats to children under 5 years of age. Little is known about the role of surface water and annual flood dynamics (flood pulse) on waterborne disease and human health nor about the expected impact of climate change on surface-water-dependent populations.Methods and findingsUsing the Chobe River in northern Botswana, a flood pulse river—floodplain system, we applied multimodel inference approaches assessing the influence of river height, water quality (bimonthly counts of Escherichia coli and total suspended solids [TSS], 2011–2017), and meteorological variability on weekly diarrheal case reports among children under 5 presenting to health facilities (n = 10 health facilities, January 2007–June 2017). We assessed diarrheal cases by clinical characteristics and season across age groups using monthly outpatient data (January 1998–June 2017). A strong seasonal pattern was identified, with 2 outbreaks occurring regularly in the wet and dry seasons. The timing of outbreaks diverged from that at the level of the country, where surface water is largely absent. Across age groups, the number of diarrheal cases was greater, on average, during the dry season. Demographic and clinical characteristics varied by season, underscoring the importance of environmental drivers. In the wet season, rainfall (8-week lag) had a significant influence on under-5 diarrhea, with a 10-mm increase in rainfall associated with an estimated 6.5% rise in the number of cases. Rainfall, minimum temperature, and river height were predictive of E. coli concentration, and increases in E. coli in the river were positively associated with diarrheal cases. In the dry season, river height (1-week lag) and maximum temperature (1- and 4-week lag) were significantly associated with diarrheal cases. During this period, a 1-meter drop in river height corresponded to an estimated 16.7% and 16.1% increase in reported diarrhea with a 1- and 4-week lag, respectively. In this region, as floodwaters receded from the surrounding floodplains, TSS levels increased and were positively associated with diarrheal cases (0- and 3-week lag). Populations living in this region utilized improved water sources, suggesting that hydrological variability and rapid water quality shifts in surface waters may compromise water treatment processes. Limitations include the potential influence of health beliefs and health seeking behaviors on data obtained through passive surveillance.ConclusionsIn flood pulse river—floodplain systems, hydrology and water quality dynamics can be highly variable, potentially impacting conventional water treatment facilities and the production of safe drinking water. In Southern Africa, climate change is predicted to intensify hydrological variability and the frequency of extreme weather events, amplifying the public health threat of waterborne d...

Influences of Land-Use Dynamics and Surface Water Systems Interactions on Water-Related Infectious Diseases—A Systematic Review

“…The influence of rainfall and stormwater runoff during winter and summer are crucial pathways of water pollution. The study identified a positive relationship between urban floods and E. coli concentration in flood retention ponds in Botswana [88]. Agricultural land use, such as the cultivation of crops, was linked to an increase in N and P in the Fuxian Lake in China [56].…”

“…Temperature, turbidity, pH Dengue [75] Temperature Malaria [59,75,87] E. coli, fecal coliform Cholera [45,61,62,81,88] E. coli, fecal coliform, turbidity, pH Dysentery [61,62,89] E. coli, fecal coliform Typhoid fever [61,62] E. coli, fecal coliform, BOD, temperature, DO Cryptosporidiosis [70,81] Fecal coliform Schistosomiasis [76,77,83,85,[90][91][92] E. coli, fecal coliform, temperature, turbidity Buruli ulcer [85] E. coli, fecal coliform, temperature, DO, BOD, TSS, turbidity Hookworm [92] pH = Potential of Hydrogen; DO = Dissolved Oxygen; BOD = Biochemical Oxygen Demand; TSS = Total Dissolved Solid.…”

“…Water plays a major role in the emergence and transmission of infectious diseases, through direct and indirect pathways [81]. In 2017, flooding in Botswana resulted in an increased concentration of fecal coliforms in the downstream sections of the Chobe River, which contributed to an increase in reported cases of diarrheal diseases by 16.7% with a four weeks lag among children under five years [88]. Areas with high population density, frequent flooding, bare-soils, and built-up areas were linked to higher reported cases of cholera and typhoid in Semarang City in Indonesia [27].…”

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“…In contrast, the net decrease in excess morbidity was lower for RCP2.6, which assumes a limited increase in global average temperatures of 2°C following climatechange adaptation and mitigation policies (van Vuuren et al 2011b). Although a recent study in Africa has reported that climate change may increase diarrheal disease outbreaks (Alexander et al 2018), the direction and magnitude of this impact on morbidity may in fact differ in areas. There is insufficient knowledge about climate effects on different types of diseases, and our results emphasize the importance of further investigations into projections of global warming and the associated impacts on mortality and morbidity due to different pathogens.…”

The impact of rainfall on drinking water quality in Antananarivo, Madagascar

“…A poor capacity to provide safe drinking water, regardless of weather conditions, is of growing concern in low-income areas vulnerable to climate change [1,2]. Indeed, under global forecasts, some parts of the globe will experience increased frequency and intensity of rainfall [3] with increasing difficulties to limit storm impacts, such as flooding or increased run-off [4,5].…”