I'd wash your hands and change your clothes between each set of bunnies. If they would be going out in the same room, pick up poops, and swap out litter pans. It may be troublesome, but some bunnies (mine included) can get very aggressive or scared when they smell a strange bunny. When we first brought Joshua home, Toshi would fly into a rage, attack us, and let out some bunny odors :? He will still do this if I don't change my clothes after coming home from the shelter...