According to scholars at the University of Paris, the Black Death is created on this day in 1345, from what they call “a triple conjunction of Saturn, Jupiter and Mars in the 40th degree of Aquarius, occurring on the 20th of March 1345”. The Black Death, also known as the Plague, swept across Europe, the Middle East and Asia during the 14th century, leaving an estimated 100 million dead in its wake.
The Black Death is estimated to have killed 30% – 60% of Europe’s population, reducing the world’s population from an estimated 450 million to between 350 and 375 million in 1400. This has been seen as having created a series of religious, social and economic upheavals, which had profound effects on the course of European history. It took 150 years for Europe’s population to recover. The plague returned at various times, killing more people, until it left Europe in the 19th century.
The mechanism by which Y. pestis was transmitted was established over the next decade and was found to involve the bites of fleas whose midguts had become obstructed by replicating Y. pestis several days after feeding on an infected host. This blockage results in starvation and aggressive feeding behaviour by the fleas, which repeatedly attempt to clear their blockage by regurgitation, resulting in thousands of plague bacteria being flushed into the feeding site, infecting the host. The bubonic plague mechanism was also dependent on two populations of rodents—one resistant to the disease, who act as hosts, keeping the disease endemic, and a second who lack resistance. When the second population die, the fleas move on to other hosts, including people, thus creating a human epidemic.