After analyzing 54 published studies of Old World skeletons, researchers have concluded that syphilis originated in the New World as a non-sexually transmitted disease and then mutated into a venereal version after it arrived in Europe in the 1490s.
This theory -- that syphilis crossed the Atlantic from west to east instead of the other way around -- has been around for decades, but some scientists still debate the origins of this disease which continues to have a major global health impact. The ongoing conversation reinforces the importance of understanding how diseases spread -- both in the past and today.
"This is probably one of the first examples of European diseases contracted from Native Americans," said George Armelagos, a bioarchaeologist at Emory University in Atlanta. "It's a really good example of the globalization of disease. It's showing that this is not a modern problem. It's been happening for 500 years."
Modern syphilis is a sexually transmitted disease that’s spread by a bacterium called Treponema pallidum. As of 2006, there were 36,000 cases of syphilis in the United States, according to the Centers for Disease and Prevention, with millions more cases around the globe.
But scientists have yet to fully agree about how it all started, Amrelagos said, with arguments beginning soon after Columbus’ return to Europe was followed in 1495 by a syphilis outbreak in Italy -- the first documented epidemic of the disease in the Old World.
Since then, some researchers have argued that syphilis bacteria had long been present in Europe at low levels, and that some unknown force triggered an outbreak in the late fifteenth century.
Others, including Armelagos, argue that the only skeletons showing evidence of infection with syphilis before 1492 were in the New World.
At the heart of the debate are questions about the accuracy of both dating and diagnosing ancient skeletons. Treponema infections leave telltale pits and scars on skulls and thickening of bones. But other diseases can cause those kinds of signs, too. And syphilis is just one of at least three diseases caused by various kinds of Treponema bacteria.
For the new study, Armelagos and colleagues re-analyzed 54 published reports of treponemal disease in the Old World before Columbus set sail. Where details were vague, the researchers also contacted study authors for photographs and other information.
Not a single report of pre-Columbian syphilis in Europe, they concluded in the Yearbook of Physical Anthropology, included enough information to confirm a diagnosis of the disease. There is evidence, on the other hand, of the syphilis in the New World dating back at least 7,000 years.
Those findings echo what University of Kansas paleoosteopathologist Bruce Rothschild concluded two decades ago. He said that his team has found that a diagnosis of treponemal disease in a single skeleton has, at best, a 70 percent chance of being correct.
And there remains no standard, reliable technique for making posthumous diagnoses of syphilis. At one New World site, for example, different studies have estimated the prevalence of anywhere from zero to 100 percent of skeletons affected by the disease.
Settling questions about how diseases have spread in the past could have future public health implications.
"One can look at syphilis, HIV, AIDS," and other diseases, Rothschild said. "If we understand how they spread, it gives us insight into how to manage diseases and bring them under control today."