Syphilis and Christopher Columbus have more in common than you might think: they set foot on new continents and colonized the natives in the late 15th century (Columbus - the indigenous people of the Americas, syphilis - the Europeans). In addition, both the sailor and the disease were looking for a way to reach Asia.
Syphilis first broke out in Europe in 1494 in a French army camp, a year after Columbus returned from a voyage to the Americas. The disfiguring disease spread among soldiers and their sexual partners, causing sores on the genitals, rectums or mouths.
In just five years, syphilis spread throughout Europe. Soon after, it reached India, China and Japan. Sex, although not the only way the disease is transmitted, is an effective way to spread it.
According to the so-called “Columbus hypothesis“, syphilis was brought to Europe by sailors returning from colonizing the indigenous peoples of the Americas. The idea is that diseases were exchanged between Europeans and Americans, just as new goods are exchanged: gunpowder for tomatoes; smallpox for syphilis.
A new study published on December 18, 2024 in the journal “Nature“, provides support for this hypothesis.
Kirsten Boss of the “Max Planck“Institute for Evolutionary Anthropology“ in Leipzig has conducted a genetic analysis of five skeletons found in South America. They give the team reason to conclude that an ancestor of the bacteria that causes syphilis was present in the Americas 8,000 years ago.
“Four of the five skeletons analyzed date back to before 1492, which means that this pathogenic diversity was already present in North and South America by the time Columbus arrived there,“ says the study's author.
Syphilis originated 8,000 years ago
To test the Columbus hypothesis, Boss and her colleagues genetically analyzed bacteria in bone wounds in the five skeletons, which originated in Chile, Argentina, Peru and Mexico.
Their bacterial samples included three subspecies of the treponema family. One of them, Treponema pallidum (T. Pallidum, also known as pale treponema in Bulgarian), causes modern syphilis.
Researchers from Bos' team compared the genetic differences of older treponema subspecies with modern syphilis samples, and the data allowed them to extrapolate the time required for the bacteria's evolution, and thus estimate when the pathogen appeared.
Their analysis confirms that the syphilis-causing bacterium T. pallidum originated from an 8,000-year-old ancestor, precisely at the time of Columbus. "Our model suggests that syphilis first emerged around 500 or 600 years ago, either in the Americas or in Europe (or elsewhere) from a bacterial strain brought from the Americas," says the study's lead author.
How did syphilis spread around the world?
The study provides strong evidence that T. pallidum was widespread in the Americas before Columbus arrived from Renaissance Europe. Yet it does not prove definitively that syphilis was brought to Europe from the Americas, only that "North and South America acted as a reservoir in which [the syphilis bacteria] circulated. It is possible that they came to Europe from elsewhere or were already there," says Matthew Beale, a genomics expert at the Wellcome Sanger Institute in Cambridge, UK. Beale was not involved in the study.
Studies suggest that treponemal diseases may have been endemic in northern Europe at the same time as Columbus' voyages, and perhaps even earlier.
The exact origin of syphilis is difficult to prove, says Kertu Mayander, an archaeogeneticist at the University of Basel in Switzerland. One hypothesis is that treponemal diseases have always existed, being transferred to humans during their migration from Asia to the Americas about 12,000 years ago.
“Another theory is that they are zoonotic, meaning they jumped from animals to humans in the Americas. "But we haven't yet found evidence of animals with treponemal diseases," the scientist says.
It's also unclear what caused modern syphilis to emerge 500-600 years ago as a highly sexually transmitted infection. "It's possible that something caused the treponemal bacterial species to recombine and cause more aggressive forms of syphilis," Mayander says.
What makes the issue even more complicated is that syphilis and gonorrhea were often conflated in historical documents, and were not recognized as separate diseases until about 200 years ago.
"There is still historical debate about whether the syphilis epidemic described in the 15th century was really caused by T. pallidum," Beale says.
Antibiotic-resistant strains of syphilis are still a problem today
Before penicillin was available, syphilis disfigured people's bodies and caused paralysis, blindness, and even death. But syphilis has not been eradicated: sexually transmitted infections account for more than 8 million new cases each year, and congenital syphilis is responsible for about 200,000 stillbirths. Syphilis cases are also increasing among young people, and research suggests that this may be linked to an increase in unprotected sex.
There are also strains of T. pallidum that are resistant to antibiotics, which means that the risk of new, deadly syphilis infections is increasing.
That's why studies like this are important, says Kertu Mayander. “Our study shows that syphilis is able to adapt to any environment. It also raises the question of whether other treponemal diseases existed before and whether new, more aggressive diseases may emerge in the future."