Black death can return

US scientists warn that the plague that once killed 75 million people worldwide could re-occur in the future.

Black death was the name of plague in Asia and Europe from the 14th century to the 18th century. The outbreak broke out more than 100 times in Europe during this period. This is one of the most terrible pandemics in human history. Scientists say it kills 75 million people in the world, from 25 to 50 million people in Europe.

About 800 years ago, Justinian plague broke out in the Eastern Roman Empire in 541 and 542 AD and spread to many other areas. Historians estimate that about 25 million people died because of it.

Illustration of pandemic Black Death in Europe in the 14th century. (Photo: blogspot.com)

Discovery said that scientists have long suspected that a bacterium called Yersinia pestis causes Black Death.

Dave Wagner, a professor at Northern Arizona University's Microbiology Center in the United States, warns that plague can cause great trouble for people in the future.

"We all know that Y. pestis bacteria have been transmitted from mice to humans in the past. Today they are still hiding in rat bodies in many parts of the world. If plague can break out in humans and spread on wide area and then disappear, that means it can re-export , " Wagner said.

Wagner and his colleagues took samples of Y. pestis bacteria from the remains of the victims of pandemic Justinina in Bavaria, Germany for analysis. They also used DNA in the bones of the victims to erect the entire genetic code of the bacteria. They then compared that gene to today's plague-causing agents.

The results showed that the bacteria causing Justinian pandemic were very different from the bacteria that caused the Black Death. But the bacteria that cause the next pandemic - starting in Hong Kong and spreading throughout the world - are most likely the "descendants" of the bacteria that caused Black Death. Of course, the level of danger of bacteria causing a pandemic is much higher than that of Justinian.

Professor Hendrik Poinar, an ancient DNA expert, thinks that Wagner's discovery is both interesting and confusing.

"We need to answer a question: Why did the plague that killed millions of people suddenly disappear?" , Poinar said.

One theory is that humans have evolved to better deal with bacteria so the level of destruction of plague decreases. In addition, Wagner remarked that it is possible that the climate has changed in a way that is detrimental to bacteria, making it impossible to survive as easily as before.