I started a new game in winter and my character started occasionally to cough, even if there was no sick moodle.
Maybe its related to the fact that NPC's become sick (because they are not prepared for winter, they are all dressed in summer clothes, im not surprised they get sick) and the dialogue is showed to the player.
Its a little annoying, I hope someone can fix this.
(Zombies cant hear you, so its just a writed speech).