Infection

Getting hit by a Hupia (monster) melee has a chance to infect you. You can see if you are infected and the severity by the dark green veins at the edges of your vision. Succumbing to the infection will turn you into a monster and you will lose control of your character.

You can see if another player is infected by looking at their face. If they have dark green veins, they're infected.

Eating Mushrooms with [Left Click] will keep the infection at bay, but will not cure you. An antidote (most commonly found in Locked Medical Cabinets) will cure it completely.

You can [Right Click] while holding an Antidote to stab another player with the needle and cure their infection.