MedPlag The medieval plagues: ecology, transmission modalities and routes of the infections

Abstract

The goal of the project is to better understand the mechanisms underlying the transmission of plague caused by Yersinia pestis in Europe and beyond during Medieval times and its routes of dissemination. To do this, we resort to a multidisciplinary approach involving history, genomics and ecological studies. The results of an extended work on the ecology of the second pandemic (1346-18th c.), published in PNAS 2015 (Schmid et al. 2015), have gained a large amount of attention. Its main message—that plague was continuously reintroduced into medieval Europe from Asia and not established in local reservoirs—was inferred by integrating ecology, paleoclimatic tree-ring records, and medieval epidemiology, and links back to the distribution of current-day genetic variation of Y. pestis. This revolutionary hypothesis, is now widely accepted as one of the leading theories for the second plague pandemic and sets forward predictions about the genetic relatedness of plague strains of the Black Death and later waves to be tested using ancient DNA techniques. For this purpose, we have collected a large number of samples of putative plague victims, which span a time of 12 centuries, and we are analyzing them with state of art techniques to obtain ancient genomes of the pathogen. Additionally, we have started an epidemiological work, which combines simulations and historical records to understand how putative modes of plague transmission differ in crucial epidemiological characteristics..