I think most of, if not all "The Others" basically have the opposite of the sickness or infection.
"The Others" seem to be just a group of followers that will all do whatever it takes to protect the island and do Jacob's will at all costs, which seems like the opposite of what the MIB is trying do.
I think "the others" all died at some point, just like Ben as a child ("He'll always be one of us") and were healed in the temple spring water (before Jacob's death and MIB seemingly infected it) and they came back different. I'm not sure how different but I'm guessing part is that they lose their free will.
I think room 23 and that mind control stuff was "the others" way to prepare the younger ones to accept being "cleansed". Which literally meant drowning them in the spring water (which was clean at the time) so they can be changed.