I have two examples.
One is avian influenza. We know that simply by walking through a puddle that a bird had pooped in and then walking into a barn, the number of viral particles introduced into that barn was extraordinarily low, yet it went down with pathogenic avian influenza. It doesn't take much with certain diseases.
The other thing is porcine epidemic diarrhea. Trying to get rid of that disease and clear it from manure slurry is not a conversation you want to have—