The virus enters the CNS by ascending along the peripheral nerves from the wound site. The incubation period usually between one and three months depends on the distance between the wound and brain. External examination of brain shows intense edema and vascular congestion. There is widespread neuronal degeneration and inflammatory reaction that is more severe in the brain-stem. The dorsal root ganglia, spinal cord and basal ganglia may also be affected. Rabies virus can be detected within Negri bodies by immunohistochemical and ultra-structural methods.
As the infection advances, the affected individual exhibits extraordinary CNS complications, with slightest touch being painful and producing violent motor responses or even convulsions. Contraction of pharyngeal create aversion to swallowing even water. The symptoms include :headache, malaise and fever though with local paresthesia around the wound is diagnostic.