Why is it so easy for birds to spread illness?

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Benjamin Anderson |

TED-Ed

• September 2026

While avian influenza used to infect mostly birds, in the past few years, it’s been found in over 70 mammal species, including cats, dairy cows, foxes, seals, and bears. Each new mammalian infection gives the virus more chances to drift or shift, spill over into humans, and ignite a pandemic. So, what is it about H5N1 that makes it so frighteningly flexible? Benjamin Anderson investigates. [Directed by Anton Bogaty, narrated by Addison Anderson, music by Jarrett Farkas].