I mean it's a typical Walking Dead non-reveal. That's why the show is so goddamned terrible. They lampshaded it two weeks ago with the whole "I don't see any bites" "Maybe it's scratches" "I don't see any scratches" "Must be scratches" "OK, it must be scratches" scene. It was just a matter of time before the dipshit characters figured it out, though it goes without saying that the doctor at the CDC probably should've mentioned the methods of transmission at some point in all his bullshit, pre-suicidal research.