Study Reveals Plague’s Evolutionary Strategy to Survive Three Pandemics

Recent research indicates that the bacteria causing the plague evolved to become less lethal over time, allowing it to infect people during three distinct pandemics over more than a thousand years.

The Plague of Justinian: A Two-Century Crisis

The first pandemic, known as the Plague of Justinian, occurred in the 6th century at the beginning of the Middle Ages and lasted about 200 years.

The Black Death, which began in the mid-14th century, was the deadliest pandemic in human history, wiping out up to half the population in Europe, Western Asia, and Africa, with outbreaks persisting for centuries.

The third bubonic plague pandemic started in China in the 1850s and continues today, with cases still reported in parts of Africa.

“Given the historical importance of the plague bacteria, it is crucial to understand how these outbreaks spread,” explained Javier Pizarro-Cerda, a microbiologist at the Pasteur Institute in France and co-author of the study published in the journal Science.

Evolution Toward Lower Virulence

The researchers analyzed samples of the bacterium Yersinia pestis from each pandemic. In all cases, the bacterial genes evolved to become less virulent and deadly over time.

By causing milder infections, the bacteria likely extended the duration of the pandemics, as this increased their chances of spreading between people.

Lab Evidence Backs the Theory

To confirm this theory, the team infected rats with recent bacterial samples and observed that with reduced virulence, the disease lasted longer.

Although antibiotics now effectively combat the plague, this study may help us understand how other pandemics might evolve.

This allows us to better understand how pathogens adapt to different conditions,” said Pizarro-Cerda. “We now have a clearer understanding of what plague is and how we can protect ourselves against it.

Read the original article on: Science Alert

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