Is that a universal truth, or is it historical? Situational? This virus is said to spread well before a person even knows they're infected. A mutation could simply extend that period. Or it could increase the degree to which it is contagious without affecting mortality, right? Or are you saying that this simply doesn't happen in the real world? Flu viruses only mutate with regards to lethality, and only in a way that works against its overall impact?