Bird flu is raging on a Utah mink farm. It could spark a human pandemic, experts say, but officials won’t act

For that to happen, this bird flu would likely need to find an intermediate host — an animal vulnerable to viruses that infect both birds and humans. Then, for that strain to jump across species, it would have to have access to humans and time to spread among them undetected.

These animals would be crowded together, each infection raising the odds that a new strain could arise through mutation.