Bird flu is infecting some chicken farms in the US. When a farm is infected, it will infect nearly all the chickens, and the government requires killing all the chickens to hinder spread to other farms.

If that were the only way the virus can spread, this would be an effective way to stop the spread. But it may be useless while wild birds continue to spread the virus.

I wonder, therefore: if we let those chickens live, would a few of them, resistant to the virus, survive and recover? Would that lead to resistant breeds?