Modalities, preferential trajectories and explanatory factors of the spatio-temporal diffusion dynamics of cholera epidemics in the Democratic Republic of Congo (DRC).

Abstract

Cholera is a severe acute diarrheal disease caused by cholera toxin-producing strains of the bacterium Vibrio cholerae. The burden of disease and death due to cholera is very high in sub-Saharan Africa. The Democratic Republic of the Congo (DRC) is one of the most affected African countries. Cholera is endemic in the eastern part of the country due to the presence of areas bordering the Great Lakes of the African Rift. These areas are the points of origin of epidemics that spread to other neighboring and distant areas. However, the understanding of the dynamics of cholera epidemic spreading remains unclear due to the variability of their spatio-temporal patterns and their explanatory mechanisms. This doctoral research was conducted to describe the spatio-temporal diffusion patterns of cholera epidemics, identify their preferential trajectories and determine the factors that modulate them.Based on the literature review (1973-2018) and the identification of spatio-temporal clusters of suspected cholera cases (2000-2018) at the health zone level using the Kulldorf retrospective space-time scan statistics, four modalities of spread of cholera epidemics from the endemic eastern lake areas were described according to the main geographical areas affected or crossed: Eastern endemic provinces and other non-endemic provinces in the East, Center, and West. Preferential epidemic routes were inferred from the directionality of the spatio-temporal clusters of cases. For the major epidemics that reached the western part of the DRC, other spatio-temporal diffusion patterns were identified along the Congo River, moving from southwestern to northern epidemic foci. Furthermore, the different models applied in this study suggest that the risk of a major cholera epidemic spreading 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