Scientists find that the bacteria behind the plague evolved to be less deadly

South China Morning Post

4 days ago

Research has found that the bacteria that cause the plague evolved to become less deadly over time. This allowed it to continue infecting people in three separate pandemics over more than 1,000 years.
The first plague pandemic struck in the 500s and lasted for around 200 years.
The Black Death began in the mid-1300s. It was the deadliest pandemic in human history. It killed up to half of the people in Europe, western Asia and Africa, with outbreaks continuing for centuries.
The third plague pandemic broke out in China in the 1850s and continues today, with some cases still being recorded in parts of sub-Saharan Africa.
'It's important to know how these outbreaks spread,' said Javier Pizarro-Cerda. He is a microbiologist at France's Pasteur Institute and co-author of a study published in May.
Pizarro-Cerda and his team studied Yersinia pestis, the bacteria that cause the plague. They looked at samples from every time the pandemic happened.
In all three cases, the bacteria evolved to become weaker and less deadly. By causing less severe infections, the bacteria likely made the pandemics last longer, giving them more opportunity to spread from person to person.
The researchers confirmed this theory by infecting rats with recent plague samples. They found that if the plague was less harmful, the rats stayed sick for a longer time.
While antibiotics can now fight off the plague, the research could help us understand how other pandemics might evolve. This will allow scientists to come up with better ways to protect humans from future plagues.