I do. If I was a survivor in any sort of post-apocalyptic situation in which everything and everyone I know and love is gone, I would probably have a complete mental breakdown.
This, half the people here, or all, would not last knowing that everyone they know are infected beings. I probably would end up having a mental breakdown also, I would not have the mental strength to deal with that.
Also if you watched The Walking Dead, *spoiler alert* when that one black guy in the Sheriff's town tried to shoot his undead wife, he hesitated a forget ton, that is what would happen if you were to shoot someone you have known for years, not to mention a loved one.
Sorta Off Topic: If the post-apocalyptic situation is zombies, I would have a mental breakdown, if it was a nuclear fallout, probably not. I would be close to one but not as bad, because ya know, I won't have to fight off people I have known.