The Black Death, also known as the Great Mortality, is one of the deadliest pandemics to have ever taken place in human history. It is responsible for the deaths of hundreds of millions of  people. This largest mortality event is conjectured to have been the upshot of plague caused by the bacterium Yersinia pestis

It is believed that humans initially contracted this bacterium from infected rodents through the bite of fleas. Then ultimately it started running frenziedly in human population and turned into the most lethal pandemic ever recorded. 

The Triumph of Death by Pieter Bruegel the Elder, depicting the results of Black Death.
The Triumph of Death by Pieter Bruegel the Elder, depicting the results of Black Death. [Wikimedia Commons]

It is without question that our DNA sequencing technology has achieved quite a remarkable feat, yet the advancement is not adequate enough to slenderize the elusory nature of this plague’s genesis.

In an effort to gain better insight on its origin and movement, researchers conducted comprehensive analysis of more than 600 genome sequences of Yersinia pestis, encompassing the genomes from strains of the plague that first appeared in humans 5,000 years ago, the plague of Justinian, the mediaeval Black Death and the current Pandemic, which emerged in the early 20th century. 

The analysis revealed that Y. pestis has an erratic molecular clock. This peculiarity makes it   difficult to mark out the rate at which mutations accumulate in its genome over time, which are then used for calculating dates of emergence. 

Genomic sequences found throughout the globe, despite being separated by years, are all identical and this is indicative of the fact that the pathogen has a rather tedious pace of evolution. This creates enormous challenges to either determine the route of transmission or to pinpoint its exact origin.

To address these challenges, researchers came up with a noble approach to single out specific populations of Y. pestis, which would facilitate their attempt to identify and date five populations throughout history, including the most ancient strain of the pandemic that had emerged centuries before the pandemic was catalogued in Europe. 

The approach in question being accurate reconstruction of pandemics of the past, present and future, and for which genetic evidence alone is not sufficient. It calls for historical, ecological, environmental, social and cultural contexts. 

With all these elements at disposal, scientists believe they would be able to properly reconstruct the timing and spread of short-term plague pandemics, which can be particularly useful for upcoming research related to past pandemics and the evolution of the ongoing COVID-19 pandemic and other similar outbreaks.  

The study has been published in the journal Communications Biology.