Abstract
Despite recent insights into cholera transmission patterns in Africa, regional and local dynamics in West Africa-where cholera outbreaks occur every few years-are still poorly understood. Coordinated genomic surveillance of Vibrio cholerae in the areas most affected may reveal transmission patterns important for cholera control. During a regional sequencing workshop in Nigeria, we sequenced 46 recent V. cholerae isolates from Cameroon, Niger, and Nigeria (37 from 2018 to 2019) to better understand the relationship between the V. cholerae bacterium circulating in these three countries. From these isolates, we generated 44 whole Vibrio cholerae O1 sequences and analyzed them in the context of 1280 published V. cholerae O1 genomes. All sequences belonged to the T12 V. cholerae seventh pandemic lineage. Phylogenetic analysis of newly generated and previously published V. cholerae genomes suggested that the T12 lineage has been continuously transmitted within West Africa since it was first observed in the region in 2009, despite lack of reported cholera in the intervening years. The results from this regional sequencing effort provide a model for future regionally coordinated surveillance efforts. Funding for this project was provided by Bill and Melinda Gates Foundation OPP1195157.
Highlights
Molecular characterization of seventh pandemic Vibrio cholerae has led to new insights about global cholera transmission and has highlighted the important role of transmission within and between Asia and Africa (Weill et al, 2017)
We found no evidence for a new introduction of V. cholerae O1 from outside of West Africa between 2014—the date of the last previously published isolate from these countries—and 2018
This finding is based on the fact that all newly sequenced isolates from 2018 to 2019 fall within the T12 lineage, which was present in West Africa from 2009 to 2014
Summary
Molecular characterization of seventh pandemic Vibrio cholerae has led to new insights about global cholera transmission and has highlighted the important role of transmission within and between Asia and Africa (Weill et al, 2017). Epidemiological data suggest outbreaks across this region may be connected (UNICEF, 2013a; UNICEF, 2013b; UNICEF, 2013c), but the nature of recurring outbreaks in the region has yet to be understood It is unclear if cases go unreported in years between outbreaks or if each represents a distinct pandemic V. cholerae introduction from outside the region. Conclusions: Phylogenetic analysis of newly generated and previously published V. cholerae genomes suggested that the T12 lineage has been continuously transmitted within West Africa since it was first observed in the region in 2009, despite lack of reported cholera in the intervening years. The results from this regional sequencing effort provide a model for future regionally coordinated surveillance efforts.
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