Bubonic Plague: Black Death Pandemic Could Fine-Tuned the Immunity Genes of its Survivors

The Black Death, also known as the bubonic plague pandemic of the mid-1300s, was a global outbreak caused by an infection from the bacterium Yersinia pestis.

The deadly outbreak ravaged Western Eurasia and North Africa. It is considered to be the most fatal pandemic in human history, killing approximately 75 to 200 million people due to severe or lethal symptoms which had no cure at that time.

In summary, the Black Death pandemic devasted Afro-Eurasia and killed approximately almost half of the world's human population during the mid-14^th century, according to prevailing historical records and modern studies. One of the most infamous and grueling symptoms of the bubonic plague disease is the development of one or more swollen lymph nodes or "buboes" that are painful.

The onset of the bubonic plague pandemic was believed to have originated from the bite of an infected flea carried by rats. These infected rodents were reportedly once aboard a ship coming from the Crimea region and Asia, which docked in Messina, Sicily. Most of the sailors on the vessel were dead and those who survived had black boils that ooze blood and pus on their bodies and were extremely ill.

Several centuries after the historic pandemic, a new study led by Canada reveals that the evolution of immune genes is linked with the Black Death. In particular, researchers involved in the study assert the medieval pandemic set the stage on how humans respond to disease of today. This finding is based on the fine-tuned immunity genes of survivors of the bubonic plague pandemic.

Immunity Genes

The new research was published in the journal Nature on Wednesday, October 19, wherein researchers from the McMaster University in Hamilton, Ontario, led the breakthrough discovery that infectious disease like the Black Death pandemic is among the strongest selective pressures triggering human evolution.

The research team arrived at their conclusion regarding the relation between the bubonic plague pandemic and the immunity genes through historic genetic analysis. For instance, the team analyzed centuries-old DNA from survivors and victims of the said pandemic by identifying important genetic differences which determined who lived and died hundreds of years ago.

The analysis also revealed that descendants of those people who were exposed from the Black Death pandemic also carried an aspect of the genes into their own immune system, as mentioned by the non-profit organization American Association for the Advancement of Science (AAAS).

Black Death Pandemic

As was mentioned earlier, the bubonic plague is a bacterial infection mainly found in rodents and associated fleas, which readily jumps to humans during close physical contact. Plague outbreaks are the most devastating epidemics in history. In contemporary times, cases of plague still emerge in different parts of the world, including the United States or China, where a case was reported in Mongolia.

However, the disease is no longer deadly as it used to be, likely due to the immunity genes and the antibiotics of today. Despite our knowledge of the disease, the origins of the bacteria-driven bubonic plague still remain a mystery even for hundreds of years, according to National Geographic.