A refined phylochronology of the second plague pandemic in Western Eurasia.

The origin and spread of consecutive outbreaks of the second plague pandemic in Europe (14th to 18th c.) are still poorly understood, although over one hundred ancient Yersinia pestis genomes and a vast corpus of documentary data have been collected. For most ancient genomes, radiocarbon (RC) dates regularly spanning more than 100 y are the only temporal information. This hampers an association with historically recorded outbreaks and limits our understanding of the microevolution and phylogeography of Y. pestis in the four centuries following the European Black Death (1347-1353). Here, we present new genomic evidence of the Second Pandemic from 11 sites in Europe, yielding 11 full and 15 lower-coverage genomes of Y. pestis dating to 1349-1710. To improve the dating information of our newly sequenced and previously published Y. pestis genomes, we present "Phylogenetically Informed Radiocarbon Modeling", an approach that integrates chronological information retrieved from phylogenetic analysis with respective RC dates, leading to more accurate and precise dating intervals. Together with a fine-grained analysis of recorded plague outbreaks, this allows us to tentatively associate 75 genomes of the Second Pandemic with historically documented plague outbreaks.