Plague: How the plague could ravage so devastatingly

Plague: How the plague could ravage so devastatingly



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It was a disaster. The doctors note that there has never been such a mass extinction before. While the deceased are hastily buried in graves, many people believe that the end of the world has come. Some practice as little as possible to increase the chances of a place in heaven, others live as if there was no tomorrow. Everything that was in order before breaks apart. From then on, the year 1347 stood for one thing above all: the plague. The plague, then known as "The Black Death", comes across the Mediterranean and rages so strongly that in many areas only every second survives.

The dangerous infectious disease plague has been with mankind for millennia and has repeatedly led to devastating epidemics with millions of deaths in the past. Researchers have now discovered that the plague pathogen has existed for much longer than previously thought. In a more harmless form, this was apparently already common among people in the Bronze Age.

"Black Death" is one of the worst epidemics in history
The plague is one of the most devastating epidemics in human history and led to terrible epidemics, especially in the Middle Ages. But the infectious disease, also known as "black death", apparently appeared at least 3000 years earlier than previously thought. Because like an international team of researchers led by Eske Willerslev from the University of Copenhagen in the journal "Cell"
shows, the pathogen can be traced back to the Bronze Age almost 5000 years ago.

Bubonic plague usually arises from stings of infected fleas
However, it can be assumed that the plague bacterium Yersinia pestis did not yet pose a major risk to humans, the scientists report in a press release from the publisher "Cell Press". Instead, it only used the possibility of using fleas as carriers in the first millennium BC. Because the plague is actually a disease of wild rodents such as mice, rats or squirrels. But their parasites can also carry the plague pathogen and spread it through stings under the rodents.

In this way, people can also become infected with the so-called "bubonic plague": the flea stings an infected host, picks up the plague bacterium and passes it on again. As a result, transmission from one person to another is also possible, which can quickly lead to a dangerous epidemic or pandemic. Plague sepsis can also arise if bacteria enter the blood through a flea stitch. The lung plague, however, is mostly passed on from person to person through droplet infection.

Researchers find traces in the examined teeth
The researchers had examined the teeth of 101 people for genetic traces of the bacterium Yersinia pestis, which came from excavations or museums, the message. Most of the individuals had lived in Europe and Asia during the Bronze Age. Finally, in seven cases, the scientists were able to detect the pathogen, which had been people who had lived between 2794 and 951 BC. The first historically documented pandemic is the “Justinian plague”, which spread from Constantinople through numerous Mediterranean ports to the Rhine in 541–767.

"Protective gene" can only be detected from the year 951 BC
In order to be able to understand the development of the bacterium, the researchers then examined 55 specific genes, which play a central role in the pathogenic properties of the bacterium. The result: With the early pest pathogen found, the so-called “ymt gene” could not be detected, by which the pathogen is otherwise protected from fleas in the intestine. Accordingly, the scientists would assume that Yersinia pestis was not initially transmitted via parasites, the report said. Since the ymt gene could only be detected from the year 951 BC, it was probably only the later form of the plague bacterium fleas that was used as an intermediate host to trigger the disease.

Although the early form of the pathogen was less dangerous in comparison, the researchers believe that it could possibly be responsible for the large population movements in the Bronze Age in Europe and Asia, the scientists suspect. Because at that time people could have fled the outbreak of the disease or repopulated areas where previously an epidemic had claimed many victims.

Pest claimed 50 million lives in the 14th century
The pathogen then spread quickly. From the first millennium BC, the formerly relatively harmless bacterium eventually developed into one of the deadliest pathogens that humanity has ever been confronted with, the scientists explain. Because in the 14th century alone, about 50 million people fell victim to the plague, according to the World Health Organization (WHO).

"The study changes our perspective on when and how the plague affected human populations and opens up new opportunities to study the evolution of diseases," said study leader Willerslev. "In addition, our study changes the historical understanding of this extremely important human pathogen and makes it possible that other so-called epidemics such as the plague from Athens and Antonine could have been caused by Yersinia pestis," adds co-author Simon Rasmussen from the Technical University Denmark in Lyngby.

If left untreated, the plague is usually fatal
However, the infectious disease has not yet been conquered, but still occurs locally in Africa (e.g. Madagascar, Congo), Asia (e.g. Russia, Kazakhstan, India) and America (e.g. Peru, southwestern USA). If the disease is not treated with antibiotics in good time, it is usually fatal. In 2013, according to the WHO, of 783 people worldwide, 126 died.

“The underlying evolutionary mechanisms that made the evolution of Y. pestis possible are still effective today. And knowing more about it will help us to understand how future pathogens can develop or how their danger increases, ”says Simon Rasmussen (nr)

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