if (when?) it happened to us, first action we would take (as a preparation) would be sealing the person in a secure 'room' so that the .. for some reason the word 'shredding' (or exorcism, if you'd like, but I realize that has negative conotations to some of you) comes to mind, can take place securely. it would be beneficial as well to keep the person alone untouched by the outside influence for awhile just to make sure you're not just providing a a vessel for another to corrupt.

depending on what kind of infestion happened, then we would choose a suitable executioner to 'divide' (or cleanse) the person, with another one supervising and to react if anything unexpected happen / the influence decide to take malicious form/ otherwise~

after that, treating the wounds left and making the person rest-- still in secure condition. then see what happens.