From the fourteenth to the seventeenth century Europe was affected by bubonic plague. One of the countries hardest hit was England with many cases concentrated in London, due to the population density and overcrowding. The plague of 1665-1666 was the last major outbreak of bubonic plague and it killed nearly a quarter of London’s population.
Bubonic plague is an infection that enters through the skin and infects the lymph system. Other forms of plague are septicemic plague and the pneumonic plague.
During excavation works for London’s new Crossrail service, a Great Plague burial pit was unearthed (the Bedlam burial ground.) The pit contained thousands of skeletal remains and these have proved to be of interest to archaeologists and biologists.
The responsible bacterium has remained a matter of debate between biologists. Now the identity of the causative pathogen has been conclusively conformed. Testing in Germany has confirmed the presence of DNA from the Yersinia pestis bacterium.
The bacterium seemingly evolved several thousand years ago from a far more benign, gut dwelling bug called Y. pseudotuberculosi (one of a group of relatively benign intestinal diseases). However, it has never been conclusively proved to have been the cause of the ‘Great Plague.’
It is generally assumed that the plague was spread by rats (or, more accurately, the plague bacterium is contained within the guts of fleas, which spread it to people when a person is bitten). The main vector for allowing fleas to spread was probably rats.
The researcher behind the recent identification, Dr. Michael Henderson, told BBC Science how the skeletons were examined: “They’re carefully boxed, individual elements, legs separately, arms separately, the skulls and the torsos.”
He adds: “We excavated in the region of three and a half thousand skeletons, one of the largest archaeologically excavated to this date. A vast data set that can give us really meaningful information.”
Identifications at the Max Planck Institute for the Science of Human History were performed by molecular palaeopathologists in order to pinpoint preserved microbial DNA. The finding is pending publication in a peer-reviewed journal.
