Yersinia pestis branch 2.MED

Branch 2.MED carries biovar Medievalis, defined by glycerol fermentation together with the inability to reduce nitrate. Its present-day distribution is central Asian, in the rodent foci around the Caspian.

The name records a nineteenth-century hypothesis rather than a genomic result, and it is the source of a persistent confusion worth stating plainly: the genomes recovered from second pandemic burials do not fall within this branch. Ancient genomes from Black Death victims sit basal to the divergence that gave rise to 2.MED, so the biovar name should be read as a historical label attached by phenotype, not as evidence that this branch caused the medieval pandemic.