To be fair, lice are pretty icky. Never had em myself, knock on wood. And I think there was an article posted here within the last couple days of chemical resistant lice showing up in Florida, among other states. So...
My daughters were on a staff at a Christian youth camp a few summers ago. One of the kids rolled in with lice and it got missed in the head check they do on check in. Pretty soon, nearly the entire camp was infected.