Paul Gans recently posted an interesting message to Mediev-L, an academic mailing list.
A whole bunch of people from a whole bunch of collaborative institutions (this is my excuse for not properly citing the article at the bottom of this post) published an article on their research into the causal organism for The Black Death of 1347-50 in Europe, “Distinct Clones of Yersinia pestis Caused the Black Death.”
Basically, through DNA analysis they found that variants of Yersinia pestis was the pathogen responsible for the Black Death. I’m not an epidemiologist (the closest is hearing classmates in college gripe about their epidemiology course) and am not going to detail the argument. However if you’re interested in the debate over the cause of the Black Death, this seems to provide pretty strong evidence that it was the Bubonic Plague and Y. pestis.
If you look at Table 1 you’ll see that their examination was not strictly limited to the 14th century but that the evidence for Y. pestis is much stronger for that event than for the Justinian plague. Someone more familiar with microbiology will have to explain their discussion from page 5 of the PDF before I understand it exactly.
I’ve never been particularly convinced by arguments that something else was the cause but this article appears to refute it fairly strongly.
BTW – as a caution, and a reminder that I am indeed The Master of the Blatantly Obvious I think there will still be individual disease events in communities that were not caused by the plague. There were plenty of other diseases affecting communities during the Middle Ages and I’m sure that when plague was raging, at times the Bubonic Plague received credit for some of them. No reason there won’t be inconsistencies in accounts and in some cases a village will probably have been affected by something else.