Why does that matter?
Countries are in a position where that number will never matter if they can prevent it from becoming one of the number of flu viruses that are in the public domain. Why should we not peruse that total prevention???
That's really what makes me mad WRT OUR official reaction to this. We can be part of the prevention of it being just another flu that we all have to deal with, but instead of doing that, people like you question how deadly it really is- which then marginalizes the effort we could put into not getting into the public domain.
So stop that, and help prevent future economic problems due to X% population getting this every single year in the US.