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Study: Ancient DNA Reveals Pre-Columbian Leprosy in Americas

Published MAY 30 2025

Story

Above: Gillis W. Long, Hansen's Disease Center — Leprosarium. Image credit: Najlah Feanny/Contributor/Corbis via Getty Images

The Facts

Scientists have discovered that a second species of leprosy-causing bacteria, Mycobacterium lepromatosis, was present in the Americas at least 1,000 years before European colonization, challenging the long-held belief that leprosy was introduced solely by European settlers.
EL PAÍS English
EurekAlert!
Researchers analyzed DNA from nearly 800 samples, including ancient human remains from Canada and Argentina, and found evidence of M. lepromatosis in three pre-Columbian individuals — dated to approximately 1,000 years ago — separated by over 12,000 kilometers (7,456 miles).
PHYS
New Scientist
EurekAlert!
The study, published Thursday, revealed that M. lepromatosis diverged from the more common M. leprae about 1 million years ago and has been evolving in the Americas for nearly 9,000 years, suggesting a long history of human-pathogen interaction on the continent.
New Scientist
Science
The research suggested that M. lepromatosis strains discovered in British red squirrels in 2016 originated from an American lineage introduced to the British Isles in the 19th century.
Institut Pasteur
ScienceDaily
Gizmodo
Modern analysis identifies M. lepromatosis in 34 individuals across multiple countries. Most cases were detected in Mexico, indicating the bacterium's continued presence and evolution in contemporary populations.
EL PAÍS English
Institut Pasteur
New Scientist
The study was conducted in collaboration with Indigenous communities, who were involved in decisions regarding ancestral remains and the interpretation of data. Materials were returned when requested, and data were shared through ethical platforms.
PHYS
ScienceDaily

Sources Split

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The Spin

Narrative A

The discovery fundamentally transforms the world's understanding of disease patterns in pre-Columbian Americas. The presence of M. lepromatosis across vast distances suggests the existence of sophisticated networks of human contact and movement throughout the continent. The findings demonstrate that complex diseases were already established in Indigenous populations long before European contact, challenging Eurocentric narratives of disease introduction.

Science

Ancient-Origins

Narrative B

While this discovery reveals pre-Columbian leprosy, it doesn't diminish the significant impact of European-introduced M. leprae, which became the dominant strain after colonization. The rapid displacement of native M. lepromatosis by M. leprae following European contact demonstrates the profound biological and epidemiological changes that accompanied colonization.

EurekAlert!