Are we still talking about the same people that were affected by one or multiple severe conditions in the first place? If so, I still don't see how that would apply to everyone else to the degree of civilizational collapse you alleged.
Not that it matters that much, people will be dying the way things develop, this way or another.
We're talking about average, healthy, young adults. There are people dying in their early 20's now in Italy. All that anyone can say for sure is that they don't know. It could have stages, it could morph into something like what AIDS is to HIV, we really don't know. It's too new and too novel.
But once this thing burns off (which it will eventually) the world is still going to be much different than it was when we were all told to stay inside. That part is kind of exciting to me.