Gene sequencing, from which scientists can gather hereditary data of organisms, has revealed that the Black Death, often referred to as The Plague, which reduced the world’s total population by about 100 million, originated from China over 2000 years ago, scientists from several countries wrote in the medical journal Nature Genetics. Genome sequencing has allowed the researchers to reconstruct plague pandemics from the Black Death to the late 1800s.

Black Death and The Plague – the plague is an infectious disease caused by a bacterium called Yersinia pestis. The Black Death is one huge plague event (pandemic) in history.

The Black Death is known as one of the deadliest and widespread pandemics in history. It peaked in Europe between 1348 and 1350 and is thought to have been a bubonic plague outbreak caused by Yersinia pestis, a bacterium. It reached the Crimea in 1346 and most likely spread via fleas on black rats that travelled on merchant ships. It soon spread through the Mediterranean and Europe. The Black Death is thought have destroyed 30% to 60% of Europe’s population – experts say it took 150 years for Europe to recover its population size. The plague came back several times until the 19th century, when it left Europe for good. Most victims died with two to seven days of becoming infected.

The authors in this new study say the plague evolved around the area of China over 2000 years ago and spread globally several times as deadly pandemics. They compared 17 complete plague genome sequences as well as 933 variable DNA sites on a unique worldwide collection of bacterial strains (plague isolates), allowing them to follow pandemics that took place in history around the world, and to work out the age of different waves of them.

The majority of pandemics were associated with known major historical events, such as the Black Death. As none of the collections of isolates from individual scientific institutions were globally representative, the scientists explained that in order to understand the historical sources of plagues, all the institutions would have to work together.

In order to prevent bioterrorism, access to Yersinia pestis – the bacterium known to be the cause of the plagues – is seriously restricted; therefore, assembling a comprehensive collection of them is impossible. An international team of scientists from the UK, USA, Ireland, Germany, Madagascar, China and France had to collaborate for a decentralized analysis of DNA samples.

Their findings reveal a detailed history of the pandemic spread of a bacterial disease in a way never seen before.

Pandemic infectious diseases have affected humans ever since we set foot on this planet, the authors explain. They have shaped the form of civilizations.

The researchers reveal that the plague bacillus developed near or in China, and via multiple epidemics was transmitted through several different routes, such as into West Asia through the Silk Road and Africa between 1409 and 1433 by Chinese travelers under explorer Zheng He. The Black Death made its way through Asia, Europe and Africa from 1347 to 1351, and probably brought the world’s then 450 million population down to 350 million. Approximately 50% of China’s population perished, while Europe’s went down by a third and Africa by an eighth.

University of Cork communiqué writes:

The last plague pandemic of 1894 spread to India and radiated to many parts of the globe, including the USA, which was infected by a single radiation still persisting today in wild rodents. Detailed analyses within the USA and Madagascar showed that subsequent country-specific evolution could be tracked by unique mutations that have accumulated in their genomes, which should prove useful to trace future disease outbreaks.

Project leader, Professor Mark Achtman, Department of Microbiology, based in the Environmental Research Institute in University College Cork, Ireland, said:

What I felt was so amazing about the results is that we could link the genetic information so accurately to major historical events.

“Routes of transmission of the plague from Hong Kong since 1894.” ( Map)

“Yersinia pestis genome sequencing identifies patterns of global phylogenetic diversity”

Giovanna Morelli, Yajun Song, Camila J Mazzoni, Mark Eppinger, Philippe Roumagnac, David M Wagner, Mirjam Feldkamp, Barica Kusecek, Amy J Vogler, Yanjun Li, Yujun Cui, Nicholas R Thomson, Thibaut Jombart, Raphael Leblois, Peter Lichtner, Lila Rahalison, Jeannine M Petersen, Francois Balloux, Paul Keim, Thierry Wirth, Jacques Ravel, Ruifu Yang, Elisabeth Carniel & Mark Achtman

Nature Genetics

Published online: 31 October 2010 | doi:10.1038/ng.705

Written by Christian Nordqvist