Theories of the Black Death

A number of epidemiologists from the 1980s to the 2000s challenged the traditional view that the Black Death was caused by plague based on the type and spread of the disease.

The bubonic form of the plague has a mortality rate of thirty to seventy-five percent and symptoms include fever of 38–41 °C (101–105 °F), headaches, painful aching joints, nausea and vomiting, and a general feeling of malaise.

The uncharacteristically rapid spread of the plague could be due to respiratory droplet transmission, and low levels of immunity in the European population at that period.

[citation needed] Historians who believe that the Black Death was indeed caused by bubonic plague have put forth several theories questioning the traditional identification of Rattus sp.

A 2012 report from the University of Bergen acknowledges that Y. pestis could have been the cause of the pandemic, but states that the epidemiology of the disease is different, most importantly the rapid spread and the lack of rats in Scandinavia and other parts of Northern Europe.

[8] University of Oslo researchers concluded that Y. pestis was likely carried over the Silk Road via fleas on giant gerbils from Central Asia during intermittent warm spells.

[11] Pneumonic expression of Y. pestis can be transmitted by human-to-human contact, but McCormick states that this does not spread as easily as previous historians have imagined.

The plague(s) had killed a large portion of the human host population of Europe and dwindling cities meant that more people were isolated, and so geography and demography did not allow rats to have as much contact with Europeans.

Greatly curtailed communication and transportation systems due to the drastic decline in human population also hindered the replenishment of devastated rat colonies.

[14] In 1984, Graham Twigg published The Black Death: A Biological Reappraisal, where he argued that the climate and ecology of Europe and particularly England made it nearly impossible for rats and fleas to have transmitted bubonic plague.

He proposed, based on a reexamination of the evidence and symptoms, that the Black Death may actually have been an epidemic of pulmonary anthrax caused by Bacillus anthracis.

Last, Cohn presented evidence displaying that individuals gained immunity to the Black Death, unlike the modern plague, during the fourteenth century.

[21] In 2001, Susan Scott and Christopher Duncan, respectively a demographer and zoologist from Liverpool University, proposed the theory that the Black Death might have been caused by an Ebola-like virus, not a bacterium.

In 2000, Didier Raoult and others reported finding Y. pestis DNA by performing a "suicide PCR" on tooth pulp tissue from a fourteenth-century plague cemetery in Montpellier.

In 2003, Susan Scott of the University of Liverpool argued that there was no conclusive reason to believe the Montpellier teeth were from Black Death victims.

[28] Also in 2003, a team led by Alan Cooper from Oxford University tested 121 teeth from sixty-six skeletons found in 14th century mass graves, including well-documented Black Death plague pits in East Smithfield and Spitalfields.

[31] In October 2010 the journal PLoS Pathogens published a paper by Haensch et al. (2010),[32] a multinational team that investigated the role of Yersinia pestis in the Black Death.

The paper detailed the results of new surveys that combined ancient DNA analyses and protein-specific detection which were used to find DNA and protein signatures specific for Y. pestis in human skeletons from widely distributed mass graves in northern, central and southern Europe that were associated archaeologically with the Black Death and subsequent resurgences.

The authors concluded that this research, together with prior analyses from the south of France and Germany Significantly, the study also identified two previously unknown but related clades (genetic branches) of the Y. pestis genome that were associated with distinct medieval mass graves.

However, surveys of plague pit remains from the Netherlands town of Bergen op Zoom showed that the Y. pestis genotype responsible for the pandemic that spread through the Low Countries from 1350 differed from that found in Britain and France, implying that Bergen op Zoom (and possibly other parts of the southern Netherlands) was not directly infected from England or France in AD 1349, suggesting that a second wave of plague infection, distinct from those in Britain and France, may have been carried to the Low Countries from Norway, the Hanseatic cities, or another site.