One branch of a deadly pathogen's family tree may have ended centuries ago, but from its ancient traces researchers can read a lineage with links to the modern world.
An international team of scientists has discovered that two of the world's most devastating pandemicsthe plague of Justinian and the Black Death, each responsible for killing as many as half the people in Europewere caused by distinct strains of the same pathogen.
The strain that helped bring an end to the Roman Empire faded out on its own about 1,500 years ago. But the other, which flourished 800 years later, led to worldwide re-emergence in the late 1800s and is still with us today, killing thousands each year.
The findings suggest a new strain of bubonic plague could emerge again in humans in the future.
"This is the oldest bacterial genome ever produced," said Dave Wagner, an associate professor in the Center for Microbial Genetics and Genomics at Northern Arizona University. "We were able to go back in time and find something that went extinct."
Wagner said the Justinian strain, which earlier research traced to having its origins in Asia, lies "smack between" two groups that are still found in China. "So that's pretty interesting that it moved all the way to Europe and went extinct. It could still be out there somewhere between Europe and China but we haven't seen it yet."
The plague of Justinian struck in the sixth century and is estimated to have killed between 30 million and 50 million people virtually half the world's population as it spread across Asia, North Africa, Arabia and Europe. The Black Death struck about 800 years later with similar force, killing 50 million Europeans between just 1347 and 1351 alone.
Researchers from NAU provided the overall plague expertise on the project, while those in the lab at McMaster University in Canada sequenced minuscule plague DNA fragments from the 1,500-year-old teeth of two victims
|Contact: Eric Dieterle|
Northern Arizona University