Phylogeogrphy Reveals Expansion Of Yellow Fever Virus Genotypes In West And Central Africa

Yellow Fever virus remains the most medically significant Arbovirus in Africa, with the occurrence of large outbreaks with human fatalities in recent years in Africa. Molecular epidemiology has shown the presence of 4 genotypes circulating across Africa; however, paucity of data still exists regarding directional spread and phylogeography of the African Yellow fever genotypes. The need to fill this gap with information from spatiotemporal data from continuous occurrence of YF outbreaks in Africa conceptualized this study; which aims to investigate the most recent transmission events and directional spread of YF virus using updated genomic sequence data. Archived Yellow Fever sequence data was utilized along with epidemiologic data from outbreaks in Africa, to analyze the case/fatality distribution. Phylogeograhic analysis was also utilized to demonstrate the ancestral introduction and geographic clustering of YF genotypes in Africa. Directional spread and geographic transmission of YF was also investigated. African YF genotypes were found to be geographical distinct, circulating within distinct geographical boundaries. Spatiotemporal spread however revealed an eastward spread of the West African genotypes over time, and recent northward movement of the East African genotype. We conclude by recommending expanded human/ vectoral surveillance of YF and other Arboviruses of public health importance, and upscaling sequencing capabilities of new and existing public health labs in Africa to help in the defense against public health threats.