The Sunday Read: ‘Animals That Infect Humans Are Scary. It’s Worse When We Infect Them Back’

Mink farms threaten to become a source of new coronavirus variants — and an object lesson in how “spillback” can make deadly diseases even deadlier.

Narrated by Soneela Nankani

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There’s a working theory for the origins of Covid-19. It goes like this: Somewhere in an open-air market in Wuhan, China, a new coronavirus, growing inside an animal, first made the jump to a human. But what happens when diseases spread in the other direction?

Sonia Shah, a science journalist, explores the dangers of “spillback,” or “reverse zoonosis”: when humans infect non-humans with disease. Using the history of diseases spreading through mink farms in the United States and Europe as a focus, Shah considers the implications of spillback, and how we might minimize its future impact.

Shah considers how spillback can ignite epidemics in wild species, including endangered ones, and can ravage whole ecosystems. More worryingly, she describes how it can establish new wildlife reservoirs that shift the pathogens’ evolutionary trajectory, unleashing novel variants that can fuel new, dangerous waves of disease in humans.

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Additional production for The Sunday Read was contributed by Emma Kehlbeck, Parin Behrooz, Anna Diamond, Sarah Diamond, Jack D’Isidoro, Elena Hecht, Desiree Ibekwe, Tanya Pérez, Marion Lozano, Naomi Noury, Krish Seenivasan, Corey Schreppel, Margaret Willison, Kate Winslett and Tiana Young. Special thanks to Mike Benoist, Sam Dolnick, Laura Kim, Julia Simon, Lisa Tobin, Blake Wilson and Ryan Wegner.

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