Ancient Mycobacterium leprae genomes reveal a potential origin and dispersal of the ancestral Branch 0.

Although previous studies have examined numerous ancient Mycobacterium leprae genomes, the available strains remain concentrated in western Eurasia. Ancient genomes from eastern Eurasia have remained virtually unexplored, limiting our ability to reconstruct the evolutionary history of M. leprae. In this study, we report the first two ancient M. leprae genomes recovered from this region. Phylogenetic analyses place both genomes within the ancestral Branch 0, and the observed phylogeographical patterns are consistent with the hypothesis that this lineage originated in southern East Asia. Together, these findings expand the known ancient genomic diversity of M. leprae and suggest that population movements across the Tianshan region may have contributed to its wider dissemination.