13. History’s Most Lethal Bacterium
Yersinia pestis, a bacterium with no spores, has been fingered by modern research and scholarship as the culprit responsible for the tragic disaster that was the Black Death. According to genetic analysis, a strain of Yersinia pestis that emerged during the Black Death caused that plague. However, it did not die off at the end of that pandemic. Instead, it has lingered around ever since, mutating and reemerging periodically to cause further illnesses and plague outbreaks.
The most recent major outbreak, known as the Modern Plague or the Third Pandemic, erupted in China in the mid-nineteenth century. It was carried by rats aboard steamships all over the world, and killed an estimated 10 million people.