Signs and Symptoms of Rabies
Rabies is an acute encephalomyelitis that almost always progresses to coma or death within 10 days after the first symptom, characterized by neurological dysfunction, behavioral changes, and specific phobias like hydrophobia and aerophobia. 1
Clinical Presentation
Rabies typically progresses through several distinct stages:
Early Signs (Prodromal Phase)
- Fever
- Headache
- Malaise
- Anxiety or agitation
- Pain or paresthesia at the bite site
- Nausea
- Vomiting
Acute Neurologic Phase (Encephalitic or "Furious" Rabies - 80% of cases)
- Hyperexcitability
- Agitation
- Confusion
- Hallucinations
- Hypersalivation
- Hydrophobia (pathognomonic) - severe spasms of the throat and respiratory muscles when attempting to drink or when presented with water 2
- Aerophobia - similar spasms triggered by air currents 2
- Autonomic dysfunction (fluctuating blood pressure, heart rate)
- Seizures
- Cranial nerve deficits
Paralytic Rabies (20% of cases)
- Flaccid paralysis beginning in the bitten limb
- Progressive ascending paralysis (may be symmetric or asymmetric)
- Can be mistaken for Guillain-Barré syndrome 2
Terminal Phase
- Coma
- Multiple organ failure
- Death (virtually inevitable once clinical signs develop)
Time Course
- Incubation period: Highly variable, typically 3-12 weeks but can range from several days to months, rarely exceeding 6 months 1
- Prodromal phase: 2-10 days
- Acute neurologic phase: 2-7 days
- Coma: 5-14 days
- Death: Almost always occurs within 10 days after the first symptom 1
Diagnostic Considerations
In humans, rabies should be suspected in any patient with:
- History of animal bite (especially from bats, raccoons, skunks, foxes, or unvaccinated dogs)
- Progressive neurologic symptoms
- Hydrophobia or aerophobia
- Rapid deterioration without other explanation
Important Clinical Pitfalls
Absence of bite history: Up to 20% of patients may not recall a bite, particularly with bat exposures where bites can be minor and unrecognized 3
Misdiagnosis of paralytic rabies: The paralytic form can be mistaken for Guillain-Barré syndrome, leading to delayed diagnosis 2
Atypical presentations: Children or individuals who received incomplete post-exposure prophylaxis may present with atypical symptoms, making diagnosis challenging 4
Post-vaccination cases: Extremely rare cases may occur despite vaccination, often with modified clinical presentation 4
Lack of hydrophobia: Not all patients develop the classic hydrophobia, especially early in the disease course
Prevention
Since rabies is almost universally fatal once symptoms develop, prevention through proper post-exposure prophylaxis is critical:
- Immediate wound cleansing with soap and water for 15 minutes
- Administration of rabies immune globulin
- Complete course of rabies vaccination
- Tetanus prophylaxis as indicated 3
Early recognition of potential rabies exposure and prompt initiation of post-exposure prophylaxis remain the only effective interventions to prevent this devastating disease.