Seems at this point in time like the strain crossing from wildlife to humans are the virulent ones, and the human-to-human are the new mutated strains. I may be wrong on how lethal these new strains may be but I stand to be corrected.
The original strain that jumps from wildlife to humans can be more easily contained by stopping bushmeat trade, like how they close and shut the seafood place that sells exotic meat.
My point is, for the new mutated strain to propagate new generations successfully, it cannot be too harsh on its host, if the new strain kills off its host too quickly, the line won’t last long. So, we shall see.