Scientists once believed Europeans brought leprosy to the American continents via infection from the bacterial species Mycobacterium leprae.

But now a new study published in the journal Science reveals that a different form of leprosy-causing bacteria — called Mycobacterium lepromatosis — was already circulating in the Americas for at least one thousand years.

Leprosy was therefore already affecting American indigenous peoples well before European colonization.

The study authors analyzed more than 800 samples taken from ancient remains in Canada and Argentina.

The genomes of the bacteria taken from the samples were reconstructed, analyzed, and dated.

Comparisons between the samples showed the bacterial genomes were of distinctive branches of the lepromatosis species at each end of the continent.

However, they remained genetically similar. This suggested that the bacteria species had spread rapidly across the Americas, probably covering the landmass........

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