It’s never been easier for animal pathogens to spill over into humans.

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Over the last 40 years, disease outbreaks among humans have become more and more frequent. The majority of those diseases are zoonoses, or diseases that originated in animals, like Ebola, West Nile virus, and probably Covid-19. But what makes zoonotic outbreaks likelier than ever is actually something humans are doing.

According to science journalist Sonia Shah, author of the 2017 book "Pandemic," the expansion of humans onto more and more of the planet’s land has increased the likelihood of disease outbreaks in two ways. First, as humans move into what were once animal habitats, we end up living closer to animals that might contain dangerous pathogens; and second, as we destroy or alter animal habitats, we’re driving away or killing off animals that once served as a “firewall” between those pathogens and us. And the human land development driving this trend shows no signs of stopping.

Correction: At 4:28 and 4:49 we mistakenly depict the European robin. The species actually responsible for the spread of West Nile virus in North America is the American robin.

Further reading:

Vox’s Sigal Samuel interviews Sonia Shah:
https://www.vox.com/future-perfect/20...

Sonia Shah’s book Pandemic: Tracking Contagions, from Cholera to Ebola and Beyond
http://soniashah.com/pandemic-the-book/

The World Health Organization’s retrospective on the 2014 Ebola outbreak:
https://www.who.int/csr/disease/ebola...

World Wildlife Fund 2018 Living Planet Report:
https://c402277.ssl.cf1.rackcdn.com/p...

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