Apparently, the New World isn't all that intrepid explorer Christopher Columbus discovered; seems we may also have him to thank for spreading the pathogen that causes syphilis—along with news of the Americas—to Europe.

A new study provides what scientists say is the most convincing evidence to date that the Italian adventurer and some of his crew contracted the disease during their voyage to the New World—and unwittingly introduced it to the old one circa 1493.

The research culminates centuries of debate over whether the disease stemmed from bacteria that originated in the Old or New worlds.

Researchers from Emory University in Atlanta report in the online journal PLoS Neglected Tropical Diseases that they used phylogenetics—the study of the evolutionary link between organisms—to study 26 geographically scattered strains of a family of bacteria known as Treponemes, which are behind the sexually transmitted disease syphilis as well as related nonvenereal infections such as yaws. They found that the venereal syphilis-causing strains arose relatively recently in humans and are closely related to an ancient infection isolated in South America that gives rise to yaws.

"That supports the hypothesis that syphilis—or some progenitor—came from the New World," said lead study author Kristin Harper, an Emory molecular genetics researcher.

According to the researchers, the origin of syphilis has been hotly debated since the first recorded epidemic of the disease in Europe in 1495. Most of the scientific evidence in recent years had been gleaned from the bones of members of past civilizations in both the Old and New worlds; bones were considered credible markers since chronic syphilis causes skeletal lesions. But skeletal analysis was hobbled by an inability to accurately determine bone age and a lack of supporting epidemiological evidence.

Another potential hitch is that Treponema bacteria cause disorders that share similar symptoms but are transmitted differently. Syphilis is sexually transmitted, for instance, whereas yaws and endemic syphilis are tropical conditions that are spread by skin-to-skin or oral contact. One hypothesis is that Treponema subspecies from the tropical Americas morphed into the more virulent venereal, syphilis-causing strains to survive in the cooler European climes.

Scientists say the study is significant because of the large number of strains analyzed, including two species of yaws found in isolated inhabitants of Guyana in South America.

"Syphilis was a major killer in Europe during the Renaissance," said co-author George Armelagos, a skeletal biologist at Emory who has been studying syphilis for three decades. "Understanding its evolution is important not just for biology, but for understanding social and political history. It could be argued that syphilis is one of the most important early examples of globalization and disease, and globalization remains an important factor in emerging diseases."