Brain Fever

This painful infection causes bleeding from the eyes and eventually blinds the victim. A beast or humanoid bit by another creature infected by brain fever must succeed on a DC 15 Constitution saving throw or become infected.
One day after infection, the creature starts to suffer from short-term madness. Once per encounter (or when activated by high stress), they must roll a Wisdom saving throw of DC 15. Upon failure, the creature spends its turn chasing after and attacking the nearest target. Three days after infection, the creature suffers extreme paranoia and has to roll with a disadvantage on Wisdom and Charisma checks. After a week, the creature goes completely feral, attacking anything that moves without any self-control.
Brain Fever can be cured using a rare flower called Hazebane, which grows in the forest. Given an hour, a character who has proficiency with an herbalism kit can turn the flower into one dose of medicine. Ingested before a long rest, one dose of it prevents the disease from worsening after that rest. After three doses, the ointment cures the disease entirely.

Encounter: Infected Animal

The players come across a pond in a small alcove. A Small or Medium beast (such as a giant weasel) will make a Stealth check against the party’s Passive Perception, then jump out of hiding in an attempt to attack the party. If it succeeds in biting someone, they must roll to resist the disease it carries: Brain Fever.

Type

Bacterial