By looking at strains of the Black Plague in ancient teeth, researchers determined a new type of the disease could reemerge.
"The research is both fascinating and perplexing, it generates new questions which need to be explored, for example why did this pandemic, which killed somewhere between 50 and 100 million people die out?" Hendrik Poinar, associate professor and director of the McMaster Ancient DNA Centre and an investigator with the Michael G. DeGroote Institute for Infectious Disease Research, said in a news release.
One strain of the disease is believed to have faded out while a second was spread throughout the world and reemerged in the 1800s. Little is known about how the relationship between the Justinian Plague (which contributed to the fall of the Roman empire) and Black Death about 800 years later. The Plague of Justinian is believed to have killed 30 and 50 million people in the sixth century; the Black Plague killed about 50 million Europeans between the years of 1347 and 1351.
Researchers were able to isolate DNA fragments of two Justinian plague victims, the fragments are considered to be the oldest-known pathogen genomes. The researchers were able to reconstruct the Yersinia pestis bacteria (which caused the plague) from the samples and compared it to modern strains.
The team found the Justinian strain was an "evolutionary dead end" but other strains formed later on during the Black Plague era. A pandemic that hit Hong Kong could have beeen related to these later strains.
"We know the bacterium Y. pestis has jumped from rodents into humans throughout history and rodent reservoirs of plague still exist today in many parts of the world. If the Justinian plague could erupt in the human population, cause a massive pandemic, and then die out, it suggest it could happen again. Fortunately we now have antibiotics that could be used to effectively treat plague, which lessens the chances of another large scale human pandemic" Dave Wagner, an associate professor in the Center for Microbial Genetics and Genomics at Northern Arizona University, said in the news release.
The evidence came from two bodies found in Aschheim, Germany that are believe to have died from the plague between the years of 541 and 543.
The team concluded the Justinian Y. pestis strain originated in Asia, not Africa as researchers previously believed. The findings also suggest the "Plague of Athens (430 BC) and the Antonine Plague (165 -180 AD)" could have been caused be emerging Y. pestis strains.
"The tick of the plague bacteria molecular clock is highly erratic. Determining why is an important goal for future research," Edward Holmes, an NHMRC Australia Fellow at the University of Sydney, said in the news release.
The study could help us better-prepare for possible future outbreaks.
"This study raises intriguing questions about why a pathogen that was both so successful and so deadly died out. One testable possibility is that human populations evolved to become less susceptible," Holmes said.
"Another possibility is that changes in the climate became less suitable for the plague bacterium to survive in the wild," Wagner said.
