Climate change and control of diarrhoeal diseases in South Africa: Priorities for action

Abstract

Weather conditions, especially temperature and precipitation, play a critical role in shaping patterns of diarrhoeal diseases. They determine the frequency of outbreaks, and the spatial and seasonal distribution of cases. Not surprisingly, it is anticipated that the burden of diarrhoeal diseases will escalate with climate change, in tandem with gradual increments in mean temperatures, but also during episodic heatwaves. The degree and nature of this escalation will, however, vary with the mix of pathogens in an area, the quality of sanitation services, food hygiene regulations and their enforcement, and the age structure of the population, among other factors. Understanding these patterns can inform the design of measures to prevent and control heat-related diarrhoea. In this editorial, we sum evidence on the heat sensitivity of enteric infections in South Africa (SA) and other parts of sub-Saharan Africa (19 studies), drawing on articles located in a systematic review (methods detailed in Manyuchi et al. [1] ), and consider the implications of these findings for control of diarrhoea in SA in the context of climate change.Several mechanisms underlie the heat sensitivity of microbes. The reproduction, growth and survival rates of most microbes rise with temperature, within certain limits. Higher ambient temperatures accelerate contamination of food across the whole food chain, from preparation, processing and storage to eventual consumption. Importantly, on hot days people spend more time outdoors, and may eat food that is unrefrigerated and is raw or cold, rather than served cooked and hot. [2] Being outdoors also raises exposure to pathogens carried by birds, and farm and wild animals. Rural areas, per se, may be especially susceptible to heat-related impacts on diarrhoea. [3] Further, dust storms, especially frequent on hot and dry days, may settle dust particles with microbial contaminants onto vegetables and other fresh produce. Importantly, if power blackouts occur during hot weather -as we are currently seeing in SA and Venezuela -the integrity of food chains can be compromised, increasing risks of contamination.While 15 of the 19 papers identified in the review reported strong connections between heat exposure and cases of diarrhoea, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] 4 found negligible or even negative associations. [18][19][20][21] This inconsistency illustrates the complexity of pathways between temperature and infectious diseases. Indeed, these correlations are seldom linear and more frequently take an inverted U-shape, where diarrhoea rates rise with temperature, plateau and then decline. Relationships may also be J-shaped, where the incidence of diarrhoea remains stable below a certain temperature threshold, beyond which there is a rapid incline. Moreover, many enteric infections have seasonal patterns: rotavirus cases, for instance, classically occur in winter and campylobacteriosis peaks in spring. [18][19][20] Seasonal patterns are not solely related to climatic factors, however...

Childhood diarrhoeal diseases in developing countries

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Too hot to thrive: a qualitative inquiry of community perspectives on the effect of high ambient temperature on postpartum women and neonates in Kilifi, Kenya

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The self-reported human health effects associated with heat exposure in Agincourt sub-district of South Africa

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