Black Death plague. Just thinking about it sends a chill down our spine. One of the most devastating pandemics in human history. It happened in the 14th century and even today, the thought of what occurred terrifies us (and that’s after living through the COVID-19 pandemic). A new study has found that the Black Death never fully disappeared.
A single gene, just one, has allowed this deadly disease to adapt and persist in some corners of the world for more than 1,500 years!! It’s called the pla gene, and it was discovered by a joint investigation from McMaster University (Canada) and Institut Pasteur (France).
So yes, this tiny gene is responsible for the survival of this disease throughout the centuries. But what… does that mean?
The Black Death Plague
Caused by the bacteria Yersinia pestis, which was mainly transmitted through fleas that lived on infected rats… but also through the respiratory route.
The Black Death caused terrible symptoms: high fever, intense pain, extreme fatigue, and the appearance of black lumps on the skin (hence the name). In most cases, death came within days.
Beyond the human tragedy, the plague had a massive impact on society: the economy was paralyzed, social and religious structures collapsed, and many ideas about life, death, and medicine changed. It was a turning point in European history. Have you read Boccaccio’s Decameron? It was much worse than the lockdown in 2020.
The bacteria that never left
The Black Death has left deep scars in human history, for good reason. From the Plague of Justinian in the 6th century to current outbreaks in Madagascar, the Yersinia pestis bacteria has caused millions of deaths throughout history.
The crucial role of the pla gene
The study, published in the journal Science, analyzed more than 2,700 DNA samples from plague victims. This study found that a single gene (the pla gene) changed its behavior over the centuries, allowing the bacteria to infect more effectively without killing immediately!!! This means the mutation gave it more time to spread through rats and humans, prolonging its existence.
Evolution as a weapon
And even though it seems incredible, all pandemics in human history (related to the plague) have been caused by the same bacteria. However, some strains disappeared and others continued on. That’s where the pla gene comes in: in its early variants, the plague was lethal in just a few days, but as outbreaks devastated human and rodent populations, the bacteria adjusted its strategy, almost like today’s companies. The less aggressive strains became more successful: by not killing as quickly, they had more time to spread!!
From human pandemic to rodent infection
Another key finding of the study is that the plague didn’t originate in humans, but in rats. Considering that hygiene was quite poor in those centuries and people slept on the floor… it’s no surprise they were in contact with rats and other animals… We could even say that humans were collateral victims of these rats…
The worst part? This cross-species adaptation helped the bacteria survive the major social, climatic, and health changes of the ancient and modern world!!!
Can it come back?
Don’t panic, but the research found current strains in Vietnam that show the same genetic mutations of the pla gene as those observed in medieval versions!!!
In other words, the adaptation strategy is still alive!!! And even though we currently have access to antibiotics and hygiene is widely practiced (except in the subway—there’s always someone with questionable hygiene in the subway), we still haven’t managed to eradicate this bacteria!
What can we learn for the future?
That genetics is incredible, and that deadly enemies… never really disappear, do they?