None of my traits supposedly causes anxiety, so whenever I have the anxiety moodle in-game, I always end up knowing I'm infected with the virus and becoming a zombie. I do not have sleep/fatigue enabled either, since I play the default multiplayer settings.
From that, I suggest to be able to sometimes have false positives on the anxiety moodle after being attacked by a zombie, as if your character is afraid of being infected in cases where he actually isn't. Currently I feel like it's too easy to tell that I'm becoming a zombie when that moodle appears, since it appears quite fast when infected.
Personally I would be anxious from any zombie attack if I was in my character's shoes, whether I end up infected or not, so I think such a change could add more excitement in terms of crossing fingers while hoping things will go well after the anxiety moodle appears.
In summary: To still have the anxiety moodle appear sometime after a zombie successfully attacks, regardless if the character is infected or not, instead of only when he's infected.