Rabies is a rapidly progressive, acute infectious disease of the central nervous system (CNS) in humans and animals that is caused by infection with rabies virus. The infection is normally transmitted from animal vectors. Rabies has encephalitic and paralytic forms that progress to death.
Rabies virus is a member of the family Rhabdoviridae. Two genera in this family, Lyssavirus and Vesiculovirus, contain species that cause human disease. Rabies virus is a lyssavirus that infects a broad range of animals and causes serious neurologic disease when transmitted to humans. This single-strand RNA virus has a nonsegmented, negative-sense (antisense) genome that consists of 11,932 nucleotides and encodes five proteins: nucleocapsid protein, phosphoprotein, matrix protein, glycoprotein, and a large polymerase protein. Rabies virus variants, which can be characterized by distinctive nucleotide sequences, are associated with specific animal reservoirs. Five other nonrabies virus species in the Lyssavirus genus have been reported to cause a clinical picture similar to rabies. Vesicular stomatitis virus, a vesiculovirus, causes vesiculation and ulceration in cattle, horses, and other animals and causes a self-limited, mild, systemic illness in humans (see “Other Rhabdoviruses,” below).
Rabies is a zoonotic infection that occurs in a variety of mammals throughout the world except in Antarctica and on some islands. Rabies virus is usually transmitted to humans by the bite of an infected animal. Canine rabies is endemic in many resource-poor and resource-limited countries and continues to be a threat to humans, particularly in Asia and Africa (see “Global Considerations,” below); endemic canine rabies has been eliminated from the United States and most other resource-rich countries. Rabies is endemic in wildlife species, and a variety of animal reservoirs have been identified in different countries. Surveillance data from 2008 identified 6841 confirmed animal cases of rabies in the United States (including Puerto Rico). Only 7% of these cases were in domestic animals, including 294 cases in cats, 75 in dogs, and 59 in cattle. North American wildlife reservoirs, including bats, raccoons, skunks, and foxes, have endemic infection, with involvement of one or more rabies virus variants in each species (Fig. 195-1). “Spillover” of rabies to other wildlife species and to domestic animals occurs. Bat rabies virus variants are present in every state except Hawaii and are responsible for most indigenously acquired human rabies cases in the United States. Raccoon rabies is endemic along the entire eastern coast of the United States. Skunk rabies is present in the midwestern states, with another focus in California. Rabies in foxes occurs in Texas, New Mexico, Arizona, and Alaska.
Distribution of the major rabies virus variants among wild terrestrial reservoirs in the United States and Puerto Rico, 2008. (From JD Blanton et al: J Am Vet Med Assoc 235:676, 2009, Centers for Disease Control and Prevention.)