Profiling the Plague

Recently, a paper was published in the proceedings of the National Academy of Sciences, the contents of which have begun to shed light on a controversy that has raged in the historical and medical communities in recent years. Responsibility for the “Black Death,” a fourteenth century pandemic that decimated an enormous portion of the population of Europe and elsewhere, once again lands squarely at the feet of the pathogen Y. Pestis, according to the recent article, after a team of scientists and scholars managed to genetically profile ancient samples of the disease.

The layperson might not find this surprising; after all, the popular perception of the event declares unequivocally that Bubonic Plague, using flea-infested rats as agents of transmission, was the scourge that laid low much of the European population. This idea finds its origins in investigations undertaken near the beginning of the 20th century by Paul-Louis Simond, but has come under fire in recent decades as techniques for evaluating and understanding epidemics have grown – and for some scholars the former explanations no longer held water. Objections to the aforementioned explanation of the Black Death (hereafter referred to as the Simond model) have taken essentially two forms, debate over the cause or root pathogen and arguments that have challenged the modalities by which the plague is said to have spread with such virulence.

Dr. Barney Sloane, a former field archaeologist for the London Museum has challenged the idea that rats, as opposed to simple human contact, were the primary method of transmission. He points out that during the initial outbreak of plague in London the spread of the disease sped up over the course of the winter, a period in which obviously no fleas could survive – an observation that in combination with other anecdotal evidence he finds disproves rats as the primary vehicle for the disease. Skepticism about the role of rats in the Black Death has led Dr. Sloane and others to postulate that a pneumonic form of the plague, if not some other pathogen, was responsible.

Debate about the causative agent of the Black Death has been the most speculative. Everything from the aforementioned pneumonic form of the plague to Ebola has been proposed. The historian Dr. Norman Cantor laid out an argument that Anthrax, in concert with opportunistic infections, manifests with symptoms more akin to the descriptions of ancient sources. These theories now seem to be dashed on the rocks, however, as a collection of scholars (building on earlier work by another team) seems to have produced incontrovertible evidence that, at least in England, Bubonic plague caused by Y. Pestis is the culprit.
The team took samples from a mass grave outside London from which to draw the genetic profile of the pathogen, only to discover that Y. Pestis is an interesting case in itself. Apparently at one time the pathogen was a mere soil bacterium, evolving into a deadly form characterized by its ability to produce grotesque symptoms in the victim, only to further evolve into its modern form – no less deadly, but exhibiting a lessening of the more visual symptoms. Y. Pestis seems to have made its evolutionary mission to confuse historians and drive epidemiologists with a taste for antiquarian inquiry to the brink of madness.

Without taking away from the significance of these recent findings, it is important to move forward cautiously. With a tool as powerful as genetic analysis, answers to the concrete questions about the Black Death seem possible, but surprises may wait to be uncovered. Years of hard work lie ahead, extending the sample size that corroborates the Y. Pestis model until such a time that we can say with our former confidence that we understand this event from a medical point of view.

More broadly, there is utility for modern people in understanding the pandemics of the ancient world. Epidemiologists consider the question of the next great pandemic to be merely one of time. Globalization has set the stage for a truly worldwide biological disaster, and it remains to be seen if institutions like the WHO will have the resources to fight this kind of war. The Black Death presents an almost unique case study, rivaled by few other outbreaks in history, of disease virtually destroying the fabric of human society in an entire region. In the end, whatever projections we create need to incorporate what we have learned, not only medically but about the social and political tendencies of human societies over whom the miasma of disease hangs. It is in this that the value of such a seemingly academic inquiry can be located.