What criteria does the virus use?
To wipe out EXACTLY half of the world's population? I find it hard to work out, on a genetic level.
Why are you here if you haven't seen the movie yet?
It's from a Dan Brown's book, don't be so sophisticated!
Juliet Parrish: You can't win a war if you're extinct!
It's not. They invented that for the movie. The book is different.
Anyway in the movie is not "exactly" but "about" half the population.