In rats people, in rats...
So are you waiting for the human testing?
There's a reason they use rats ... because generally speaking humans respond the same way as rats to most things.
Besides that, you're missing the point. Even something with a 10% fatality in human beings would absolutely wreak havoc.
But here's the thing. We know full well that the government already has these viruses, and worse, and they most likely have stuff that's gene-specific, that would wipe out just people with certain genes present (i.e. could target races of people). They probably have stuff that's, oh, say, 90% lethal to Russians but only 10% lethal to non-Russians, or Chinese or Indians or whatever.