Exploring relationships between drought and epidemic cholera in Africa using generalised linear models

Abstract

Background: Temperature and precipitation are known to affect Vibrio cholerae outbreaks. Despite this, the impact of drought on outbreaks has been largely understudied. Africa is both drought and cholera prone and more research is needed in Africa to understand cholera dynamics in relation to drought.

Methods: Here, we analyse a range of environmental and socioeconomic covariates and fit generalised linear models to publicly available national data, to test for associations with several indices of drought and make cholera outbreak projections to 2070 under three scenarios of global change, reflecting varying trajectories of CO₂ emissions, socio-economic development, and population growth.

Results: The best-fit model implies that drought is a significant risk factor for African cholera outbreaks, alongside positive effects of population, temperature and poverty and a negative effect of freshwater withdrawal. The projections show that following stringent emissions pathways and expanding sustainable development may reduce cholera outbreak occurrence in Africa, although these changes were spatially heterogeneous.

Conclusions: Despite an effect of drought in explaining recent cholera outbreaks, future projections highlighted the potential for sustainable development gains to offset drought-related impacts on cholera risk. Future work should build on this research investigating the impacts of drought on cholera on a finer spatial scale and potential non-linear relationships, especially in high-burden countries which saw little cholera change in the scenario analysis.

Keywords: Africa; Cholera; Climate change; Disease outbreaks; Droughts; Epidemiology; Public health; Vibrio cholerae.

Fig. 1

Pathways from water shortages to cholera outbreaks: suggested mechanism through which drought can lead to cholera outbreaks in Africa [2, 12]

Fig. 2

Marginal effect plots for the five selected covariates for the best-fit model, showing cholera outbreak occurrence probability

Fig. 3

Projected cholera outbreak occurrence (0–1) for the three scenarios in 2030, 2050 and 2070. Grey represents countries where covariate data was missing (Botswana, Zimbabwe, Somalia, Egypt, Eswatini, Western Sahara, Algeria, Libya and Eritrea) and therefore could not be included in the model. The map is our own work and the shapefiles are taken from [46] under CC-BY SA, allowing them to be shared and adapted

Fig. 4

Mean continental cholera outbreak occurrence for the projected period (2020–2070) using the three scenario datasets