Rabies is a severe viral disease that affects the central nervous system in humans and other mammals. Once symptoms manifest, the disease is almost always fatal. Its ancient origins have long been a subject of inquiry. Historical records and scientific evidence help shed light on where rabies first emerged.
Early Historical Records
The earliest known written account of rabies appears in the Code of Eshnunna from Mesopotamia, dating to approximately 1930 BC. These ancient laws included provisions for dog owners whose animals showed symptoms of rabies, suggesting early recognition of the disease and its transmission.
Ancient Greek scholars also documented rabies. Democritus described the disease in the 5th century BC, and Aristotle, around 322 BC, provided detailed accounts of its effects in animals, noting symptoms like aggression and avoidance of water. These descriptions confirm rabies’ devastating impact was recognized in early civilizations.
Identifying the Source Region and Original Hosts
While no single “patient zero” location is definitively identified, phylogenetic analyses of the virus’s genetic makeup point to different lineages emerging from distinct regions. For instance, some research suggests Eurasia as a likely historical source for canine rabies, while other lyssaviruses, related to RABV, have been discovered in bats in Africa.
Viral reservoirs are animal populations that maintain long-term transmission of a virus strain, central to understanding rabies origins. Bats are considered reservoir species for many lyssaviruses, including some related to rabies, worldwide. For the RABV itself, the most common reservoir species are mesocarnivores, such as dogs, raccoons, mongooses, and skunks. Genetic sequencing helps trace the evolutionary history of the virus, allowing scientists to identify common ancestors and reconstruct how different strains evolved and spread among various host species.
Pathways of Global Dissemination
The global spread of rabies from its presumed origins has been significantly influenced by human activity and natural animal movements. Human migration and trade routes, such as the ancient Silk Road, likely facilitated the movement of infected animals, particularly domesticated dogs, across continents. Dogs have historically been the primary vector for intercontinental spread of the “dog-related” rabies virus group and remain responsible for over 99% of human rabies cases globally.
Natural animal migrations and range expansions also contributed to regional dissemination of the virus. Different variants, or genotypes, of the rabies virus have distinct geographic distributions, reflecting separate historical spread events and adaptation to local host populations. For example, specific African rabies subclades are prevalent in different parts of the continent, showcasing varied patterns of spread. The global translocation of rabid dogs during periods of colonization further established the widespread distribution of rabies observed today.