This means that unless you use drugs ( Paracetoid 7g) you have a 50/50 chance of dying during that night. You won't get the distinctions for that day by dying of infection however you will get the Deaths by infection distinction which will appear on your soul.
Unlabelled Drugs do not have a chance to cure infection.
You can also become infected by eating a Meaty Bone.
Infection is one type of statuses.