Very well made.
It's rare to find something with the attention to details that this one has. I did have minor quibbles about it, but overall I found no glaring problems and several good points. Keep up the good work!
Oh, did I mention a couple of quibbles?...
Viruses should be able to do something on their own. If they run into a red corpuscle, perhaps another stat would be a % chance of automatically infecting it (call it say, virulence)? I also found that the time pressure gets fairly brutal without passive infections. Nevertheless, these pale compared to the quality that's already there.