Three children who lived in prehistoric Vietnam more than 3,500 years ago are forcing scientists to rethink one of the most contested questions in medical history: how to identify syphilis in the ancient past.
In a new study published in the International Journal of Osteoarchaeology, an international team led by Dr. Melandri Vlok of Charles Sturt University in Australia reports evidence that treponemal diseases could be passed from mother to child thousands of years ago. Congenital transmission has long been treated as a strong indicator of venereal syphilis — but the Vietnamese remains suggest other forms of the disease may have spread the same way.
Treponematosis is a group of diseases caused by Treponema pallidum and related bacteria, including syphilis, yaws and endemic syphilis. Yaws is a tropical disease that still affects more than 150,000 people and can cause permanent disability.
The researchers examined 309 individuals from 16 archaeological sites across Vietnam, spanning 10,000 to 1,000 years ago. Three young children showed diagnostic signs of congenital treponematosis — distinctive dental abnormalities and skeletal lesions. Two were recovered from Man Bac, a northern Vietnamese site where earlier studies had already found unusually high rates of treponemal disease.
Crucially, the overall pattern of infection in the population points away from venereal syphilis. Most cases occurred among children and adolescents, a pattern consistent with nonvenereal treponemal diseases that spread through skin contact rather than sexual activity.
"The epidemiology of the site strongly points toward a non-venereal form of treponemal disease. Yet we still see evidence of congenital transmission. That's the surprising part," Vlok said.
The finding matters far beyond Vietnam. For decades, researchers studying ancient remains have used congenital infection as evidence when debating whether syphilis existed outside the Americas before Columbus. If congenital transmission can occur in nonvenereal treponematoses, some cases previously labeled congenital syphilis may represent entirely different diseases.
"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."
So far, no confirmed biological or genetic evidence of pre-Columbian venereal syphilis has been found inside or outside the Americas. Genetic studies of remains from Europe and the Americas have instead revealed multiple treponemal diseases in ancient populations, underscoring how complex the evolutionary history of these pathogens may be.
The study also highlights the practical difficulties of such research. In tropical regions like Southeast Asia, ancient DNA is often poorly preserved, and destructive sampling of human remains raises ethical questions. Co-lead author Minh Tran, a PhD student at the University of the Philippines Diliman, calls for future research to work in genuine partnership with the communities connected to these remains.
Vlok argues the discovery also shows the remarkable adaptability of Treponema pallidum — and sounds a modern warning. "Treponemal diseases have a far more complex history than we once thought," she said, "especially as treponemal disease like yaws is re-emerging due to the climate crisis."
