In a word -- boring.
I have seen this type of thing done on Star Trek so many times that this episode bored me to death. Yawn. Disease tranforms the crew. Vulcan is once again immune to disease. God, this was such a boring episode. The only good moment was at the end when Acher told Phlox not to destroy the virus sample -- Archer clearly remembers everything that happened, and he knows how much survival meant to this race. But that was less than five minutes of good stuff in about 40 minutes of pure dreck.