It seems like this disease is so successful because of a significant symptom-free-but-contageous period followed by a small percentage of very serious symptoms.
That's what a pandemic needs. If it is very deadly very quickly it kills its transmission vectors before they can transmit. If it is entirely symptom free, it is very evolutionarily successful, but no one cares because there aren't any negative effects.
There is an "optimum" of disease characteristics for maximum damage and we seem to be experiencing one.
The bottom line is that it seems to be very difficult to prevent a majority of the world population from getting this disease and the result is going to be a global fatality rate of somewhere in the neighborhood of 1%.
