And/or the disease was held in some sort of abeyance as long as they remained on the planetoid. Yeah. And to leave meant a death sentence for both since the Companion couldn't servive beyond "a tiny march of days" and the disease would return and kill Hedford. But again this ignores the logic of beaming up to the Enterprise to rid her of the disease. Unless...unless the disease had progressed to a point where nothing more could be done and it was game over.^ Perhaps the magic of the planetoid also bolstered the health of the pathogen that was making Nancy sick, which counteracted any boost given to her.