Scientists have examined the genetic code of leprosy taken from 1,000-year-old skeletons.
Scientists have been able to learn more about the spread of the disease by comparing the older strains with those seen today, according to the BBC.
The researchers believe it was the medieval Crusades, a period where Christian soldiers battled for control of the "Holy Land," that originally spread the disease around the world.
People suffering from leprosy in medieval times were considered outcasts because of the severe deformities which come along with the disease. Sometimes those suffering from the affliction were even quarantined.
The recent study compared DNA from the leprosy-causing 1,000-year-old bacteria with modern day leprosy pathogens. The comparison showed one type of leprosy found in the Middle East today is the same as one prevalent in medieval times. Johannes Krause, from the University of Tübingen, Germany, who participated in the study believes this finding only strengthens the idea of the disease being spread during the crusades.
The researchers think leprosy most likely came out of Asia since the oldest known case of leprosy was found in a 4,000 year-old skeleton in India.
"This skeleton can only tell us it was present in Asia around 4,000 years ago, but we do not know where the origin of the disease is," Krause said.
There is also a strain of the disease in America similar to one of the ancient pathogens. The finding suggests the disease did not move to the U.S. with the original Asian settlers, but rather came over when Europe colonized the land.
"One really surprising finding was that the DNA was so well preserved, better than any ancient DNA I have ever studied," Krause said. "This opens up the possibility to study the evolution of the disease in much older remains, to understand how it evolved and adapted to humans.
The similarity of the pathogens is strange because most people have developed and immunity to the disease, it is almost completely eradicated in Europe.
"The beauty of studying the DNA from ancient diseases is that it enables direct comparison of the genetic composition of past and present genomes," said Helen Donoghue, from University College London, UK who did not participate in the study. "This provides direct calibration of the timescale for changes over time and enables us to look at the evolution of the pathogenic organism in relation to its human host."