Syphilis has its roots in America, but Europeans spread it all over the world

In the spring of 1495, the Italian campaign of Charles VIII of France was interrupted by an intense outbreak of an unknown disease that caused extremely high mortality rates and quickly spread throughout Europe, leaving survivors with disabilities that changed their bodies, minds, and lives.

This epidemic is interpreted as the first historical reference to syphilis. The origin of this disease has been the subject of debate for decades. The outbreak at the end of the 15th century occurred shortly after the return of Christopher Columbus and his crew from their first expeditions to America, leading some to believe that contact with new lands and people might have had something to do with the sudden appearance of the disease.

The “Colombian theory”

Although the colonizers brought many afflictions to the American continent (such as smallpox, typhoid, tuberculosis, bubonic plague, cholera, mumps, or measles, for example), wreaking havoc on native groups, syphilis is one of the few diseases that possibly made the reverse journey.

This “Colombian theory” for syphilis has gained popularity over the years, but it still has its critics. Its simple story began to crumble at the beginning of this decade as experts shifted their focus to the lesions observed in the bones of medieval Europe.

Both chronic patients and those born with an infection can develop changes in their bones or teeth, and several skeletons with these types of marks have already been found in Europe that predate 1492. This is why many researchers believe that the history of syphilis in Europe began long before Columbus.

Now, a study by the Molecular Paleopathology Group at the Max Planck Institute for Evolutionary Anthropology published in the journal *Nature* threatens to definitively answer the fundamental questions related to pre-Columbian or post-Columbian theories regarding syphilis.

The team led by Kirsten Bos and Johannes Krause has collaborated with scientists and archaeologists from various American countries. Their work has focused on the archaeological bones from these regions, where infections that left patterns of lesions similar to syphilis are evident from remote periods of time.

“We have known for a long time that similar infections to syphilis occurred in America for millennia, but it is only from the lesions that it is impossible to fully characterize the disease,” comments Casey Kirkpatrick, a paleopathologist who also contributed to the current study.

Bone pathology also cannot indicate whether the disease originated in America or arrived from Asia in the past and simply accompanied human groups during the early colonization events in America about 15,000 years ago.

Using state-of-the-art techniques, the team was able to recover and analyze five ancient genomes of the syphilis disease family from Mexico, Chile, Peru, and Argentina.

Old molecular puzzles

Computational microbiologist Lesley Sitter undertook the task of assembling the ancient molecular puzzles. “While preservation posed some analytical challenges, we were able to confidently determine the relationships between these extinct forms and the strains that impact global health today,” she explains.

What the experts at the Max Planck Institute discovered is that syphilis is part of a small family of diseases that also includes yaws and bejel, both classified as tropical diseases found in equatorial regions around the world.

Syphilis and pian in Mexico City

Rodrigo Barquera has previously worked with bones from colonial Mexico and has confirmed the presence of both syphilis and yaws in Mexico City in the 17th century. Based on the latest ancient genomic data, it is now clear that the Americas were a center of ancient diversity within this group of diseases before the arrival of Columbus.

“We see extinct sibling lineages for all known forms of this disease family, which means that syphilis, yaws, and bejel are the modern legacies of pathogens that once circulated in the Americas,” Barquera states.

“The data clearly support a origin in the Americas for syphilis and its known relatives, and their introduction into Europe from the late 15th century is most consistent with the data,” Bos adds.

Experts point out that everything seems to indicate that there was an explosion of cases of syphilis and pian around the year 1500 AD. This is likely what explains the breadth and intensity of the outbreak in the 16th century in Europe, whose global spread was facilitated by human trafficking networks and European expansions into the Americas and Africa in the following decades and centuries.

Spread throughout the world

“Indigenous American groups harbored early forms of these diseases, but Europeans were crucial in spreading them worldwide,” Bos states.

Now we just have to keep moving forward to unravel the mystery of bone lesions resembling syphilis that many claim to have identified in Europe before 1492. “The search will continue to define these earlier forms, and ancient DNA will surely be a valuable resource,” comments Krause. “Who knows what older related diseases spread worldwide in humans or other animals before the syphilis family appeared,” he concludes.