It was mentioned earlier about "Threshold" and the lizard-syndrome that Paris and Janeway developed for travelling at warp 10. By the end of the episode the Doctor had cured them and they never showed any negative effects of the transformation afterwards (you have to love Voyager
's reset button almost as much as the shuttlecraft genie).
Why didn't they just go ahead and jump to warp 10 for a second in order to get back to Earth. Once there, the Doctor could then cure all the human crew (there is nothing to saw the aliens onboard would be affected in the same way) by the same method no bother.