But in a new wrinkle, the research suggests the disease may not have been transmitted through sex until it adapted to the environment in.
"It evolved this whole new transmission mode, and it didn't take very many genetic changes," said study lead author Kristin Harper, a graduate student at. "What this tells us is that new transmission modes may evolve pretty rapidly. This is important to us today, because we're worried about things like avian influenza going from human to human."
Syphilis is usually easily treated today, typically with antibiotics such as penicillin. But U.S. health officials have failed in their efforts to eliminate it; minorities and gay men have been among those most likely to be infected.
Then there's the long-running controversy over how syphilis found its way to Europe, where it spread havoc for centuries. One theory holds that the disease was already in Europe before the explorer Columbus returned, but people didn't diagnose it correctly, Harper said.
The most familiar theory suggests that syphilis came to the Europe via frisky sailors on the Columbus expedition, and historical records suggest the disease did appear on the continent in 1495, three years after Columbus set sail for what proved to be the New World.
Harper and her colleagues tried to track the evolution of syphilis by examining genes from it and other diseases related to the pathogen known as Treponema.
The researchers looked at 21 genetic regions in strains of the pathogen from 26 parts of the world. Treponema causes syphilis and a disease known as yaws, a "flesh-eating" infection of the joints, bones and skin found in tropical regions.
According to the study authors, the results of their genetic research reveal that the syphilis strains appeared most recently and are most closely related to strains that cause yaws in South America.
But in a twist, the study results also suggested that yaws first appeared not in the New World but in the Old World, Harper said.
In essence, she said, the theory goes something like this: Yaws appeared in Africa and eventually made its way to South America and the New World as humans migrated. Then the germs made their way to Europe with the help of sailors and may have evolved into the venereal disease known as syphilis, perhaps because of different environmental conditions.
"It's especially neat when I think about contacts between Europeans and Native Americans," Harper said. "As far as diseases go, it seemed like a one-way street: Europeans brought measles and smallpox (to the Indians). But this is an example of disease going the other way. That seems kind of fair."
The findings are published in the Jan. 15 issue of the Public Library of Science Neglected Tropical Diseases.
The new research makes sense to Dr. Bruce Rothschild, professor of medicine at the Northeastern Ohio Universities College of Medicine, who's studied the evolution of syphilis by examining skeletal remains.
"It confirms everything we've done," he said. "When you've got two sets of totally different diagnostic techniques that come up with the same answer, that really increases the power of the technique."read more | digg story