Hey, so the way you should act is mostly normal, maybe having slightly altered speach/heavy or slower walk pattern but otherwise you are fairly normal until you drop.
Others should treat you as more agressive, thus weapons pointed incase you run at them to attack. Having fists out isn't an indicator of you being infected, hightened aggression is however. So you aren't KOS, you should only really be shot if acting aggressivley as is with all instances of killing someone.