Lyme bacteria settled in North America far earlier than we thought

While the Lyme disease outbreak in people dates back only about 40 years, the bacterium that causes this disease has called North America home for more than 20,000 years, according to a study published in August in the journal Nature Ecology and Evolution.

The epidemic began when a set of strange symptoms, including swollen knees and skin rashes, cropped up in people in the 1970s in Lyme, Connecticut. The disease was later attributed to the bacterium Borrelia burgdorferi. The new study unveils this bacterium’s geographic history and leads its authors to believe the current Lyme disease epidemic resulted from recent ecological changes rather than changes in the disease bacterium itself.

“The bacteria have been here for a long time in North America – long before the last ice age, long before humans even arrived,” says lead author Katharine Walter, who studies the epidemiology of microbial diseases at Yale University. “Not only has it been present, the diversity of the bacteria is also ancient.”

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