Black Death’s Origin is Identified at Last

It looks like the puzzle of the Black Death has another piece put into place: Yersinia pestis definitely played a role in the infection, though we still don’t know whether it’s the only infectious agent involved. Given how much more fatal infectious diseases can be to previously unexposed populations (smallpox, anyone?), it seems plausible that Yersinia could have been a solo player in the matter.

Yersinia has for some time been the prime suspect because some of its symptoms are similar to the Black Death. But questions were raised because modern Yersinia is a slow-spreading, rat-borne disease that is very different from the Black Death. Its DNA doesn’t explain why. “There are almost no genetic differences between the ancient and modern Yersinia,” says Krause.

He speculates that the Black Death behaved differently from modern Yersinia infection due to Europeans’ total lack of previous exposure. Another possibility is co-infection with other pathogens, a so-called syndemic. The team hopes to learn more about the evolution of human disease by probing plague pits and other ancient samples for different pathogens.

Additional pits of plague victims were recently unearthed in both Italy and England, and will hopefully provide a reasonable number of samples to test for Yersinia and other causative agents.