For decades, paleopathologists worked from a convenient rule: among the treponemal diseases, only venereal syphilis passes from mother to child. Find congenital infection in ancient bone, and you have found syphilis.
Three small skeletons excavated in Vietnam have made that rule unusable, and a fresh wave of coverage this week has pushed the finding back into circulation.
A team led by Dr. Melandri Vlok of Charles Sturt University examined 309 individuals from 16 archaeological sites across Vietnam, spanning 10,000 to 1,000 years before the present. Only three showed diagnostic features of congenital treponematosis, and all three were young children. Their remains date back at least 3,500 years. The disease that marked them was almost certainly not syphilis.
Teeth That Record an Infection from Before Birth
The evidence is dental and skeletal. Treponemal infection acquired in utero disrupts developing tooth crowns in characteristic ways, leaving permanent stigmata alongside bone lesions. Two of the children came from Man Bac in northern Vietnam, one from An Son in the south, at sites dating to roughly 4,100 to 3,300 years ago.
The findings were published in the International Journal of Osteoarchaeology in March.
Treponematosis is not one disease. It is a cluster caused by subspecies of Treponema pallidum: venereal syphilis, yaws, bejel, and pinta. They produce overlapping skeletal damage, which is precisely why researchers reached for congenital transmission as a tiebreaker.
Man Bac's Sick Were Mostly Children, and That Points Away from Syphilis
The argument against syphilis at Man Bac comes from the wider burial population rather than the three children. Earlier work at the site found unusually high levels of treponemal disease, with roughly 10% of those examined showing likely infection, and the affected were overwhelmingly children and adolescents.
That is the signature of a non-venereal disease spread by ordinary skin contact between kids, not by sexual transmission among adults. Yaws fits. Yaws still affects more than 150,000 people across the tropics and can cause permanent disability.
"The epidemiology of the site strongly points toward a non-venereal form of treponemal disease," Vlok said in a statement from Charles Sturt University. "Yet we still see evidence of congenital transmission. That's the surprising part."
The Columbus Argument Loses a Piece of Evidence
The stakes here reach into one of medicine's longest-running arguments: whether syphilis existed outside the Americas before 1492. Congenital cases in European and Asian skeletons have been used for years as evidence that it did.
If non-venereal treponematoses can also pass to a fetus, that line of reasoning collapses.
"For decades, congenital infection in archaeological remains has often been taken as strong evidence of venereal syphilis," Vlok said. "Our research shows that this assumption may not always hold true. Other treponemal diseases may also have been transmitted from mother to child." She added that "some cases previously labeled as congenital syphilis may represent entirely different diseases."
The narrower version of the claim is the defensible one, and it is the version the paper makes: congenital infection alone can no longer reliably separate venereal syphilis from its non-venereal relatives in skeletal material. That does not settle the Columbus debate in either direction. It removes one class of evidence that both camps had been using.
Worth stating carefully: the Vietnamese children do not have ancient syphilis, and the researchers do not claim they do. Nor do they prove the disease was yaws. The identification rests on lesion patterns and population epidemiology, not on a recovered pathogen. To date, no confirmed genetic evidence of pre-Columbian venereal syphilis has been identified anywhere, inside or outside the Americas.
Genetic work on remains from Europe and the Americas has instead revealed multiple treponemal diseases that circulated in the past, which is part of why the team argues the field should stop treating the question as a single origin story. The more productive question, they suggest, is how the different treponemal diseases evolved alongside human societies and shifting environments.
Tropical Soil Destroys the DNA That Would Settle It
The obvious fix is to sequence the bacterium from the bones. In Southeast Asia, that is close to impossible. Ancient DNA degrades badly in hot, humid conditions, and recovering it requires destroying part of a skeleton.
"In tropical environments, recovering ancient DNA is incredibly difficult, and destructive sampling raises important ethical questions," said co-lead author Minh Tran, a PhD student at the University of the Philippines Diliman. "Future research must move in new directions, working in genuine partnership with communities connected to these remains."
The modern relevance is not abstract. Vlok has linked a resurgence of yaws to climate pressures. And in the United States, congenital syphilis has moved in the opposite direction from most sexually transmitted infections. Provisional CDC data show nearly 4,000 newborn cases in 2024, a twelfth consecutive annual increase and nearly 700% above the 495 cases logged in 2015, even as chlamydia, gonorrhea, and the most infectious stages of syphilis all declined.
Congenital syphilis is preventable with testing and treatment during pregnancy. Pregnant patients should ask their clinician when and how often they will be screened.
Key Questions Answered
What did researchers find?
Three children buried in Vietnam at least 3,500 years ago had dental and skeletal signs of a treponemal infection acquired before birth.
Does this prove ancient syphilis existed in Asia?
No. The population pattern at the site points toward a non-venereal disease such as yaws, and no genetic confirmation exists.
Why does congenital transmission matter so much?
Researchers long treated it as a marker of venereal syphilis specifically, using it to argue about where and when syphilis originated.
What is yaws?
A non-venereal treponemal disease spread by skin contact, affecting more than 150,000 people in tropical regions and capable of causing permanent disability.
Why not just sequence the bacteria?
Ancient DNA degrades poorly in tropical climates, and sampling requires destroying skeletal material, raising ethical concerns.
Is congenital syphilis a problem in the U.S. today?
Yes. Provisional CDC data recorded nearly 4,000 cases in 2024, marking the twelfth straight annual increase, though these cases are preventable with prenatal testing and treatment.
