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

Abstract

AbstractBackgroundCholera 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 adapted the percentage attributable fraction equations to understand the proportion of cholera outbreaks attributable to conflict onset.ResultsThere were 12,829 conflict events and 1,178 cholera outbreaks during the period analysed in Nigeria and the DRC. 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. Several states/provinces with the strongest positive relationship were also areas of high reported conflict or were neighbouring states/provinces.ConclusionOur 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.