Rabies is an acute, progressive viral encephalomyelitis that primarily affects carnivores and bats, although any mammal can be affected (including humans). The disease is fatal once clinical signs appear.

Rabid animals of all species usually exhibit typical signs of CNS disturbance, with minor variation among species. The most reliable signs, regardless of species, are acute behavioral changes and unexplained progressive paralysis. Behavioral changes may include sudden anorexia, signs of apprehension or nervousness, irritability, and hyperexcitability. Incoordination, altered vocalization, and changes in temperament are apparent. Uncharacteristic aggressiveness may develop (e.g., a normally docile animal may suddenly become vicious). Commonly, rabid wild animals may lose their fear of people, and normally nocturnal animals may be seen wandering about during the daytime.

The incidence of rabies in skunks increased dramatically in Colorado in 2008. While skunks are the most common wildlife animal to carry rabies, the skunk rabies variant has spilled over to raccoons, foxes, coyotes, and mountain lions. Rabies is transmitted from infected animals to other species through a bite or by the introduction of infected saliva into a fresh wound, cut, or mucous membrane.