Though my mind may lie in doubt, it still be turned curious by this suggestion type thing
Tristan Rodberg (firstname.lastname@example.org) writes:
1) Why Hunters can't be Infected by the Flood.
As the 'Art of Halo' book calls them, essentially, they're giant cans of worms. An absolute crazy load number of worms. Infection form bites a Hunter, and realizes that he ain't gettin' nowhere. He infected one worm in the can, and can't infect anybody else, as the Hunter collective effectively jettisons the infected worm, leaving that worm to his fate as food.
Or, perhaps the infected worm is not ejected, but the Hunter collective is on a different level of consciousness then what the Flood infection form can overwhelm effectively, if at all.