Canine distemper virus (Morbillivirus canis, CDV) is a single-stranded, nonsegmented, negative-sense RNA virus and a member of the family Paramyxoviridae. Canine distemper is a highly contagious and often fatal infectious disease in dogs and ferrets. The virus is highly promiscuous and can infect many additional animals in the order Carnivora, as well as animals in other orders. The virus has been found worldwide. Though CDV is considered a single serotype, there have been many different genotypes described, named based on the location of initial detection. The virus is well-controlled through vaccination, but outbreaks do continue to occur, particularly in regions and in situations in which herd immunity is reduced or lacking. The virus is both leukotropic and epitheliotropic, resulting in immunosuppression and in multi-systemic disease, with various combinations of respiratory, gastrointestinal, and dermatological signs. The virus can also infect cells in the central nervous system and clinical signs are variable and associated with which portions of the central nervous system are infected. The disease ranges from virtually no clinical signs to severe disease and death in approximately 50% of cases in dogs. There is currently no recognized antiviral for treatment, so prevention through vaccination is key for controlling this virus.