Pathophysiology
Clinical meaning
Rabies is caused by a neurotropic RNA virus of the Lyssavirus genus transmitted through the saliva of infected mammals, most commonly via bite wounds. After inoculation, the virus replicates in local muscle cells before entering peripheral nerves at the neuromuscular junction. It travels via retrograde axonal transport to the central nervous system at approximately 12-24 mm per day. Once in the CNS, the virus replicates extensively in neurons (especially limbic system, hippocampus, brainstem), causing encephalitis that is nearly 100% fatal once symptoms appear. The incubation period ranges from weeks to months (average 1-3 months), depending on bite proximity to the CNS. The virus causes Negri bodies (eosinophilic intracytoplasmic inclusions) in infected neurons. Clinical rabies presents as furious (80%, with hydrophobia, aerophobia, agitation) or paralytic (20%, ascending paralysis). Post-exposure prophylaxis (PEP) with wound care, rabies immunoglobulin, and rabies vaccine is highly effective if initiated before symptom onset.