Modified Canine Distemper Virus is a mutated form of the canine distemper virus, which was genetically modified on purpose with the intent to kill any supernatural canine on the deadpool list. One of the assassins in the Deadpool, known only as "The Chemist", created the modified version of the canine distemper virus and used it as Beacon Hills High School after infecting Satomi's pack at some point.
Species vulnerable to the virus are supernatural canines such as werewolves, werecoyotes, and Kitsune. Malia, a werecoyote, was exposed to the virus and nearly died from it after beginning to bleed black blood from her nose, mouth, and ears, and after losing her vision completely. However, consuming wild purple Reishi Mushrooms are known to cure the virus and prevent those who ingest it from being infected in the first place.
Humans suffer some effects but will ultimately recover from it with no permanent harm.