An extinct version of the Yersinia pestis bacterium responsible for the 1347-1351 “Black Death” in which 30-50 million people in Europe died, has been discovered by evolutionary geneticist, Hendrik Poinar and team, says an article in Proceedings of the National Academy of Sciences (PNAS). The authors describe the Black Death as one of the most devastating events in the history of humankind.
Hendrik Poinar, from McMaster’s Michael G. DeGroote Institute for Infectious Disease Research (IIDR), Kirsti Bos, a graduate student at Johannes Krause of the University of Tubingen, et al used high-throughput DNA sequencing together with a novel way of DNA enrichment to make their discovery.
The researchers say that scientists had never before fully understood what caused the plague, which is still believed to kill approximately 2,000 people every year globally.
Poinar said:
“The Black Death is arguably one of the most dramatic examples ever of emerging or re-emerging disease. By studying the origin of this disease it may yield information concerning the organism’s evolutionary history as a human pathogen.
“Black death killed 50 million people in Europe in 1348 and spread from China through the Middle East to Turkey, Messina, Sicily and into the ports of Genoa and into London and then to Paris. One-third of the population of Europe died and the question in the beginning was, ‘What was the bug that started it?'”
The scientists say their study indicates that the Black Death was the second of three pandemics – the first being the Plague of Justinian 541 AD, and concluding with the modern pandemic of the 20th century.
The scientists examined the skeletal remains of 109 humans who were buried at East Smithfield, London in 1349. They found that their bodies harbored Yesrinia pestis genes after analyzing their DNA. The team also carried out DNA examinations of the remains of 10 people who had been buried at St. Nicholas Shambles, a site predating the Black Death.
According to their preliminary findings, the pathogen that caused the Black Death may be a variant that is now extinct. The bacterium was most likely extremely virulent in 1348, Poinar explained. It acted on genes that led to transmission caused by flea bites; this encouraged bacteria to reproduce in the respiratory systems of people with pneumonia.
Poinar said:
“Our next goal is to sequence the entire DNA, and I am confident that this new technique will lead to answers that will change our understanding of the history of plague and our concept of emerging and re-emerging diseases.”
The Black Death, known as perhaps the most cataclysmic pandemic in human history, reached a peak in Europe during 1248-1350. At the time, people referred to the Black Death as the Great Pestilence or the Great Plague.
Historians say it started in China and travelled along the Silk Road, reaching the Crimea in 1346.
From the Crimea it was most likely carried by Oriental rat fleas that infested the black rats that boarded merchant ships, and spread throughout Europe and the Mediterranean.
Between 30% and 60% of Europe’s population was wiped out by the Black Death. By 1400 it had reduced the world’s population from 450 million to between 350 and 375 million. It triggered a series of economic, social and religious upheavals and had a profound impact on how European history evolved. It was not until about 1550 that Europe’s population managed to recover.
Signs and symptoms of the Black Death are imprecise, but archives most commonly include the appearance of “buboes” (gavocciolos) in the neck, armpits and groin which oozed pus and bled when opened. A “bubo” is a swelling of the lymph nodes.
Italian author and poet Giovanni Boccaccio (1313-1375) wrote the following description:
“In men and women alike it first betrayed itself by the emergence of certain tumours in the groin or armpits, some of which grew as large as a common apple, others as an egg…From the two said parts of the body this deadly gavocciolo soon began to propagate and spread itself in all directions indifferently; after which the form of the malady began to change, black spots or livid making their appearance in many cases on the arm or the thigh or elsewhere, now few and large, now minute and numerous. As the gavocciolo had been and still was an infallible token of approaching death, such also were these spots on whomsoever they showed themselves.”
The majority of patients died within seven days of becoming infected. Some documents describe freckle-like spots and rashes which were probably caused by flea bites.
Written by Christian Nordqvist