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

Yennan

Ochu

et al. 2022

Preprint

Self Cite

Cholera is reported as endemic in more than 50 countries, many of which are in sub-Saharan Africa. Nigeria currently reports the second highest number of cases, with several risk factors potentially contributing to this including poverty, water, sanitation and climate. Enteric pathogens have a significant global burden, especially on children and those most vulnerable. Despite this, attention is often drawn away from these diseases, most recently to Ebola and COVID-19. To address the need for more research and focus on cholera, a covariate selection process and machine learning was used. Data for environmental (floods, droughts) and social (conflicts) extremes, along with pre-existing social vulnerabilities, were fit to time varying reproductive number in Nigeria. We analysed this both spatially and temporally and used it to create a traffic-light system for cholera transmission, highlighting potential thresholds and triggers for outbreak. Improved access to sanitation, number of monthly conflict events, Multidimensional Poverty Index and Palmers Drought Severity Index were retained in the best fit model. Varying exposure periods showed that those living in decreased poverty, with more access to sanitation were not as vulnerable to changes and offset some of the cholera risk caused by extremes. The work presented here shows the need to address these pre-existing vulnerabilities and sustainable development for disaster prevention and mitigation and improve health and quality of life.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The impact of social and environmental extremes on cholera time varying reproduction number in Nigeria

Yennan

Ochu

et al. 2022

Preprint

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“…Previous research has found several environmental and socioeconomic links with cholera, including temperature, precipitation, poverty and water, sanitation, and hygiene (WASH) ( 3,4,5 ). Furthermore, extremes of these environmental and social conditions can act as catalysts for outbreaks, such as droughts, floods, and conflicts ( 6,7,8 ).…”

mentioning

confidence: 99%

Using self-controlled case series to understand the relationship between conflict and cholera in Nigeria and the Democratic Republic of Congo

Jean

Kelman

et al. 2021

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BackgroundCholera outbreaks contribute significantly to diarrhoeal disease mortality, especially in low-income countries. Cholera outbreaks have several social and environmental risk factors and extreme conditions can act as catalysts for outbreaks. A social extreme with known links to infectious disease outbreaks is conflict, causing disruption to services, loss of income and displacement.MethodsHere, we explored this relationship in Nigeria and the Democratic Republic of Congo (DRC), by fitting publicly available cholera and conflict data to conditional logistic regression models. We used the self-controlled case series method in a novel application, to understand if an exposure period of excess risk (conflict), increased the relative incidence of cholera. We also used a sensitivity analysis to understand potential lag effects.ResultsWe found that conflict and cholera had a strong positive relationship, especially in the first week after the event, at a national and sub-national level. Conflict increased the risk of cholera in Nigeria by 3.6 times and 2.6 times for the DRC. Conflict was attributed to 19.7% and 12.3% of cholera outbreaks in Nigeria and the DRC, respectively. This was higher for some states/provinces, with a maximum increased risk of 7.5 times.ConclusionThe results found that several states/provinces with the strongest positive relationship were also areas of high reported conflict or were neighbouring states/provinces, suggesting a possible spill-over effect. Our results help highlight the importance of rapid and sufficient assistance during social extremes and the need for pre-existing vulnerabilities such as poverty and access to healthcare to be addressed. In fragile states, conflict resolution should be a top priority to avoid excess risk for both cholera and other health and social implications.FundingNatural Environmental Research Council, UK Medical Research Council, and the Department for International Development.

Cholera past and future in Nigeria: are the Global Task Force on Cholera Control’s 2030 targets achievable?

Yennan

Ochu

et al. 2022

Preprint

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Background Understanding and continually assessing the achievability of global health targets is key to reducing disease burden and mortality. The Global Task Force on Cholera Control (GTFCC) Roadmap aims to reduce cholera deaths by 90% and eliminate the disease in twenty countries by 2030. The Roadmap has three axes focusing on reporting, response and coordination. Here, we assess the achievability of the GTFCC targets in Nigeria and identify where the three axes could be strengthened to reach and exceed these goals. Methodology/Principal Findings First, historical data were analysed for cholera death rates and a range of well-established cholera risk factors (particularly those included in the best fit models), using correlation, regression, autocorrelation function and AutoRegressive Integrated Moving Averages. Next, future scenario datasets were created (based on varying degrees of socioeconomic development and emission reductions) and used to project future cholera outbreak occurrence and transmission to 2070. The two models used were a generalised linear model and a random forest model. The historical data highlighted the significant cholera burden in Nigeria and its correlation with sanitation access. The projections suggest that significant reductions in cholera cases could be achieved by 2030, particularly in the more developed southern states, but increases in cases remain a possibility. Meeting the 2030 target, nationally, currently looks unachievable and we propose a new 2050 target focusing on reducing regional inequities. Conclusion/Significance The 2030 targets could potentially be reached by 2030 in some parts of Nigeria, but more effort is needed to reach these targets at a national level, particularly through access and incentives to cholera testing, sanitation expansion, poverty alleviation and urban planning. The results highlight the importance of and how modelling studies can be used to inform cholera policy and the potential for this to be applied in other contexts.