It turns out that scarlet fever might not have come to the Americas through European colonists, as previously thought.
Researchers from Italy and the UK discovered traces of the bacterial infection in the tooth of a mummified skull.
The remains belonged to a man who lived in the high-altitude regions of present-day Bolivia between 1283 and 1383 AD.
Christopher Columbus, the Italian explorer, only set sail in 1492. So, if the DNA analysis holds true, it suggests that scarlet fever was already affecting Indigenous populations in the Americas well before European contact.
“The ancient strain contains many, though not all, of the pathogenic genes found in modern Streptococcus pyogenes strains,” microbiologist Frank Maixner, head of Eurac’s Institute for Mummy Studies in Italy, explains.
This forgotten form of scarlet fever seems to be closely linked to modern strains responsible for throat infections, having diverged around 10,000 years ago.
Most evidence points to the first people entering the Americas via the Bering Strait about 22,000 years ago, and some overlooked genomic evidence hints that S. pyogenes existed in Europe and Africa up to 4,000 years ago.
Humans might have been fighting off this infection for quite some time, and it’s possible that its spread was influenced by migration through Siberia.
“The presence of S. pyogenes across different regions and eras suggests it may have traveled with human populations, thus aiding its global spread,” the authors of the study propose.
Before modern antibiotics came to the rescue, scarlet fever was a major cause of death and disabilities in children, occasionally leading to vision and hearing impairment. Once upon a time, its symptoms were often mixed up with those of smallpox, measles, and diphtheria.
These diseases have long been categorized as ‘frontier’ illnesses, presumed to have accompanied European settlers to the Americas, wreaking havoc on populations with little immunity.
However, that story might be overly simplistic, not just regarding scarlet fever.
Recent DNA evidence from Colombia suggests that syphilis may have existed in both the Americas and Europe for thousands of years, raising questions about whether it was truly spread only through Columbian contact.
The same applies to leprosy, and now possibly scarlet fever, as well.
The ancient DNA evidence for S. pyogenes found in the Bolivian mummy’s tooth is quite fragmented and degraded, yet scientists managed to glean small pieces of information to create a genetic model.
“It’s like assembling a puzzle without knowing what the final image looks like,” microbiologist Mohamed Sarhan from Eurac explains.
This task is undoubtedly challenging, but it also means that Sarhan and his colleagues work “without modern references, allowing us to uncover new insights and recognize genetic variants that may not be around today.”
Previously, researchers analyzing ancient DNA would dismiss longer sequences, assuming they couldn’t possibly survive over time due to contamination.
This new research claims to have overcome that issue, which, as Maixner notes, “challenges the foundations of ancient DNA research.”
“We successfully showed, based on typical damage patterns, that the longer sequences are just as ancient as the shorter ones – and they provided significant insights,” Sarhan says.
A key discovery was the identification of core virulence genes in this ancient bacterial strain, which supports its classification as a throat-infecting bacterium rather than one that affects the skin.
Thanks to antibiotics, scarlet fever isn’t the life-threatening issue it used to be, although modern strains are becoming problematic, especially with rising antibiotic resistance.
Understanding where the bacterium originated and how it has progressed over thousands of years could offer critical insights for future treatments.
The findings were published in Nature Communications.
