What parasite can live dormant inside a human without affecting the host?
Intestinal bacteria? They not only are harmless but necessary to the digestive process of humans. After antibiotic treatments, they are left in a total state of disarray and need to be replenished and nurtured back to good health.
i thought about it for 51 minutes and couldnt come up with any --- though we haves germs and they are good germs --
House would know !! ;)