Wikipedia says something interesting: https://en.wikipedia.org/wiki/Plague_of_Justinian
Earlier samples of Yersinia pestis DNA have been found in skeletons dating from 3000 to 800 BC, across West and East Eurasia.[43] The strain of Yersinia pestis responsible for the Black Death, the devastating pandemic of bubonic plague, does not appear to be a direct descendant of the Justinian plague strain. However, the spread of Justinian plague may have caused the evolutionary radiation that gave rise to the currently extant 0ANT.1 clade of strains.
Thx!
Microbes have much shorter generations, which must make it more difficult to determine a parsimonious descent tree.