I think it's funny that people go around saying "NOMADS ARE SO SMART AND HUMANS ARE SIMPLE TO THEM )))" when the human genome is constantly changing, and the amount of infected is hardly enough for a -sample- group.
Consider that, given time (with the way genetics works), there could be a human who is genetically incompatible with a Nomad, no matter how much powergaming voodoo someone tires to pull off.