Joint doctoral thesis between the University of Liège and the University of Kinshasa, publicly defended with a view to obtaining the title of Doctor of Medicine (UniKin) and Doctor of Science (ULiège)

by CT Harry César Kayembe Ntumba

Summary

Cholera is a severe acute diarrheal disease caused by strains of the bacteria Vibrio cholerae producing cholera toxin. The burden of morbidity and mortality due to cholera is very high in Sub-Saharan Africa. The Democratic Republic of Congo (DRC) is one of the most affected countries in Africa. At the national level, cholera is endemic in its eastern part due to the presence of areas bordering the lakes of the Great African Rift. These areas constitute the points of origin of epidemics that spread to other neighboring and distant areas. However, understanding the dynamics of cholera epidemic diffusion still contains gray areas due to the variability of their spatio-temporal patterns and their explanatory mechanisms. This doctoral research was conducted to describe the modalities of spatio-temporal diffusion of cholera epidemics, identify their preferential trajectories and determine the factors that modulate them.

Using the literature review (1973-2018) and the identification of spatio-temporal clusters of suspected cholera cases (2000-2018) at the health zone level using Kulldorf's retrospective spatio-temporal scan statistics, four modalities of cholera epidemic diffusion from the eastern lake endemic foci were described based on the major geographical areas affected or crossed: the endemic provinces of the east and the other non-endemic provinces of the east, center and west. The preferential trajectories of the epidemics were inferred from the directionality of the spatio-temporal clusters of cases. For major epidemics that reached the western part of the DRC, additional spatio-temporal diffusion patterns were identified along the Congo River, going from the epidemic foci in the southwest to the north. Furthermore, the various models applied in this study suggested that the risk of major epidemic spread of cholera outside the endemic provinces, notably North and South Kivu, is potentiated by the exacerbation of conflicts, followed by the intensification of movements of internally displaced persons and the amplification of cholera epidemic outbreaks around the Lake Kivu basin.

This study has shown that the dynamics of cholera epidemic spread are predictable. Taking their predictive nature into account in the development and implementation of targeted control strategies will contribute to achieving the goals of eliminating this disease.