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Thursday, October 16, 2014

The Black Death Was Not Ebola


Most people assume that the fourteenth-century Black Death that quickly ravaged the western world was a bacterial bubonic plague epidemic caused by flea bites and spread by rats. But the Black Death killed a high proportion of Scandinavians where it was too cold for fleas to survive. Biology of Plagues. Evidence from Historical Populations published by Cambridge University Press, analyzed 2,500 years of plagues and concluded that the Black Death was caused by a viral hemorrhagic fever pandemic similar to Ebola. If this is correct, the future medical and economic impacts from Ebola have been vastly underestimated.  
And he goes on to cite some similar symptoms. However, Street forgets the most obvious symptom--the bubo's, or swelling of lymph nodes, that gives the bubonic plague its name.

Moreover, he relies on books and articles approximately a decade old. More recent research has confirmed that y. pestis, the bacterium that causes bubonic plague, was present in remains from not only the Black Death but the earlier outbreak termed Justinian's Plague. The New York Times reported in 2011:
After the Black Death reached London in 1348, about 2,400 people were buried in East Smithfield, near the Tower of London, in a cemetery that had been prepared for the plague’s arrival. From the teeth of four of those victims, researchers have now reconstructed the full DNA of a microbe that within five years felled one-third to one-half of the population of Western Europe. 
Advancing science: the remains of plague victims in a 14th-century London cemetery.
The bacterium that causes plague, Yersinia pestis, is still highly virulent today but has different symptoms, leading some historians to doubt that it was the agent of the Black Death.
 
Those doubts were laid to rest last year by detection of the bacterium’s DNA in plague victims from mass graves across Europe. With the full genome now in hand, the researchers hope to recreate the microbe itself so as to understand what made the Black Death outbreak so deadly.
 (See also this article at Nature). The 6th Century "Justinian's Plague" was also caused by y. pestis. However, the 6th Century strain was different from the 14th Century strain; and the 14th Century strain was different from the much less lethal version we see today.

As for the lack of dead rats, the 14th Century plague was able to be transmitted from person to person (either via human fleas or in its airborne version) and did not need rat fleas as a vector. (It is significant to observe in this regard that the rat-borne plague generally produces bubos on the legs or in the groin, due to the proximity of the location of the flea bites; but that accounts of the 13th Century plague are specific in mentioning the bubos first forming on the neck and upper torso).

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