Spearheaded by the Black Death in the fourteenth century, the second plague pandemic was a formative influence on European societies in the medieval and early modern periods. Bos et al. sequenced five osteoarcheological samples from an outbreak — the Great Plague of Marseille (1720−1722) — dated towards the end of the second pandemic. A SNP-based phylogenetic analysis showed that the Marseille outbreak was caused by a Yersinia pestis strain descended from the Black Death strain but not ancestral to any known extant strain, which suggested that this pathogenic lineage had persisted for three centuries before becoming extinct. Based on the new phylogeny, the authors argue that an uncharacterized host reservoir local to Europe or West Asia may have sustained the repeated outbreaks of the second pandemic.