According to US researchers, new genetic evidence suggests that Christopher Columbus introduced syphilis to Europe from the New World, sparking a long-standing debate about the disease's origins. Through a genetic analysis of the syphilis family tree, researchers discovered that its closest relative is a South American cousin that causes yaws, an infection caused by a sub-species of the same bacteria. Kristin Harper, an evolutionary biologist at Emory University in Atlanta, noted that some believe syphilis is an ancient disease while others think it originated in the New World. Harper's study, published in the journal Public Library of Science Neglected Tropical Diseases, concludes that syphilis or its precursor was brought from the New World to the Old World relatively recently in human history. She stated that the research provides support for the "Columbian theory," which connects the first documented European syphilis outbreak in 1495 to Christopher Columbus and his crew's return. She commented, "Our genetic data, combined with the epidemic in Naples in 1495, strongly backs the Columbian hypothesis." Syphilis, a sexually transmitted disease caused by the bacterium Treponema pallidum, begins with a sore and can progress to a rash, fever, and potentially lead to blindness, paralysis, and dementia. Recent evidence of the disease's origins has been found in skeletal remains in both the New World and the Old World, with chronic syphilis leaving distinctive lesions on bones. Harper described it as having a worm-eaten appearance during a phone interview. She utilized phylogenetics to analyze the evolutionary connections between different organisms in the Treponema family, which includes bacteria responsible for syphilis, bejel, and yaws. The study involved examining 26 strains of Treponema, including two strains of yaws from Guyana that had not been previously sequenced. Harper explained that they sequenced 21 regions in search of DNA variations among the strains. They reached the conclusion that yaws is an ancient infection, while venereal syphilis appeared relatively recently. Harper believes that a nonvenereal form of the tropical disease transformed into venereal syphilis that could survive in the cooler European climate. However, the process of this transformation is not clear. "We can only confirm that the precursor of syphilis originated in the New World, but its exact nature remains unknown," she stated. In a commentary in the same publication, Connie Mulligan and colleagues from the University of Florida challenged Harper's interpretation, arguing that her conclusions were too reliant on genetic changes observed in the Guyana samples. Mulligan proposed that more informative evidence could be obtained from DNA obtained from ancient bones or preserved tissues. Harper agrees that further research is necessary to elucidate the transmission of syphilis to the New World. "This is a blurred image," she remarked.