When discussing the black plague, many historians believe it to be the bubonic plague transmitted by fleas on rats.
I was wondering if there are any competing theories to what caused this mass death.

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  • Not all historians agree it's due to rats. At least some point to northern Scandinavia's lack of rats as counter evidence, and suggest it was likely human fleas and lice instead. – Denis de Bernardy Aug 29 '19 at 7:22
  • @DenisdeBernardy Rats are only one type of carriers of fleas. And rats did exist in Scandinavian ports for very obvious reasons. – Mark Johnson Aug 29 '19 at 7:59
  • @DenisdeBernardy Scandinavia's lack of rats was my point. Rats existed in ports arriving from the continent, possibly transfered to humans and (I assume) to dogs. So rats should not be excluded as part of the chain. – Mark Johnson Aug 29 '19 at 8:52
  • @MarkJohnson: As I understood, rats were only present in northern Scandinavia's port cities. They didn't live inland. Yet the plague struck inland areas too, suggesting a different carrier, which could have been human fleas or lice. – Denis de Bernardy Aug 29 '19 at 9:06

The most common theory is that it was Yersinia Pestis that lived in the flea Xenopsylla cheopis that live on rodents. When the sickness kills the host they flea seek other hosts. As the black rat (Rattus rattus) lived close to humans it would infect humans. Infected humans can spread it on by coughs, vomits and sneezes.

Susan Scott and Christopher Duncan published the theory that it may instead have been a type of viral haemorrhagic fever (ebola is probably the most known type).press release

Graham Twigg published The Black Death: A Biological Reappraisal (1984) that suggest that it would have been impossible for rats to spread the disease with such speed. He instead thinks it may have been anthrax. In In the Wake of the Plague (2001) by Norman F. Cantor he also suggests anthrax and cites finds from a mass grave in Scotland.

See https://en.wikipedia.org/wiki/Theories_of_the_Black_Death for further reading.

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  • the question is asking for competing theories, not the known cause. – Mark Johnson Aug 29 '19 at 8:09
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    It's worth noting that those were theories published prior to the Analysis of the DNA from plague pits in East Smithfield in 2011 - which not only confirmed that Y. pestis was the cause, but also identified the particular variant of Y. pestis. – sempaiscuba Aug 29 '19 at 13:28
  • @sempaiscuba The test showed the presence of Y. pestis, but it didn't test for anything else nor could it confirm that was actually the cause of death. – liftarn Aug 29 '19 at 14:26

Not only historians, but also medicaly one still only believes what type of bacteria was the cause of the Black death.

Black rats (which were immune) carried the fleas which themselves lived off the blood of their victims.

This blood contained the bacteria.

There are some opinions today that still have doubts about the exact cause

Your question is, if I have understood it correctly, asks what other ideas existed as to the possible cause.

The first Wikipedia artical states the following:

Medical knowledge had stagnated during the Middle Ages. The most authoritative account at the time came from the medical faculty in Paris in a report to the king of France that blamed the heavens, in the form of a conjunction of three planets in 1345 that caused a "great pestilence in the air". This report became the first and most widely circulated of a series of plague tracts that sought to give advice to sufferers. That the plague was caused by bad air became the most widely accepted theory. Today, this is known as the miasma theory.

Bad air was deemed the main cause of all illnesses, where the medical practitioners didn't have faintest clue of what the cause was.

In fiction, a good source for alternative ideas may be the book

It is about the life of a Christian English boy in the 11th century who journeys across Europe in order to study medicine among the Persians.

I found this book (which starts in 1020) very interesting for 3 reasons

  • how peaple lived and traveled in Europe at the time
  • how religion effected (both Christian and Muslim) the study of Medicine
    • not much change between the 11th and 16th century
    • the similarly of the illegal medical study found in The Agony and the Ecstasy is striking
  • how learned medical people fought to gain knowledge (instead of just accepting the bad air theory)

It is this major portion of the book (about 10%, which the Wiki book plot summary skips altogether, but delt with in the film plot) that deals with the Black plague and what the cause of it could be.
The film, of course, shows all of the gruesome details extensively.

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  • Analysis of DNA from plague pits in East Smithfield has not only confirmed that Y. pestis was the cause, but also identified the particular variant of Y. pestis. – sempaiscuba Aug 29 '19 at 4:55
  • @sempaiscuba yes and I believe in France they have also found reliable remains. But the main part of the question is asking about alternatives - thus the reference. – Mark Johnson Aug 29 '19 at 5:01

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