What are the signs and symptoms of rabies?

Rabies Signs and Symptoms

Rabies presents as an acute, progressive encephalitis with two distinct clinical forms: furious (encephalitic) rabies in 80% of cases characterized by pathognomonic hydrophobia, and paralytic (dumb) rabies in 20% of cases presenting as ascending flaccid paralysis. 1

Incubation Period

• The incubation period typically ranges from 1-3 months but can vary from several days to over a year, with an average of one to two months 1, 2
• In domestic animals, the incubation period is generally 3-12 weeks but can range from several days to months, rarely exceeding 6 months 3

Prodromal Stage (Early Symptoms)

• Non-specific constitutional symptoms including malaise, fever, and headache occur early in the disease course 4
• Paresthesias or pain at the bite site is a characteristic early finding that helps distinguish rabies from other encephalitides 5
• Signs of local wound healing may be present during this early stage 4

Furious (Encephalitic) Rabies - 80% of Cases

Cardinal Features

• Hydrophobia is pathognomonic for rabies: terror and violent spasms of the inspiratory muscles, larynx, and pharynx precipitated by attempts to drink water or even by the sight or sound of running water 1, 5
• Aerophobia: similar spasms triggered by air currents or drafts 6
• Intermittent episodes of agitation, hyperexcitability, and bizarre behavior alternating with periods of lucidity 1

Neurological Manifestations

• Disorientation progressing to stupor and coma 1
• Patients become extremely agitated in the presence of stimuli such as loud noises, air currents, and running water during the acute neurologic phase 1
• Episodes of generalized arousal or hyperexcitability 6
• Hallucinations and maniacal behavior may occur 5

Autonomic Features

• Hypersalivation (excessive drooling) 5
• Tachycardia 5
• Hyperpyrexia (high fever) 5

Paralytic (Dumb) Rabies - 20% of Cases

• Ascending flaccid paralysis resembling Guillain-Barré syndrome, starting from the bitten extremity 1, 6
• Progressive lower motor neuron weakness 6
• Sphincter involvement and sensory disturbances 5
• Death from respiratory and bulbar paralysis occurs after a longer illness than furious rabies 5
• In a minority of cases, hydrophobia may develop before terminal coma 5

Clinical Signs in Animals

• Clinical signs of rabies in animals include inappetance, dysphagia, cranial nerve deficits, abnormal behavior, ataxia, paralysis, altered vocalization, and seizures 3
• Progression to death is rapid in animals 3

Disease Progression and Prognosis

• Death typically occurs within 7 days of symptom onset 1
• Rabies is not considered curable once clinical symptoms appear, with only 6 documented human survivors, and 5 of these had received vaccination before symptom onset 1, 7
• Paralysis and coma supervene after a few days in furious rabies; survival rarely exceeds seven days 5

Diagnostic Imaging Findings

• MRI may show nonenhancing focal lesions in basal ganglia, thalami, and brainstem 1

Important Clinical Pitfalls

• Paralytic rabies is frequently misdiagnosed as Guillain-Barré syndrome, particularly when there is no clear history of animal exposure 8
• Focal neurological abnormalities are surprisingly uncommon despite severe encephalitis 5
• The brainstem is preferentially involved in both clinical forms, though there may be no obvious clinical signs of brainstem dysfunction 8
• When a patient is comatose, cardinal signs like hydrophobia may be lacking, making diagnosis challenging 8

Management Focus

• When a definitive diagnosis is obtained, primary health considerations should focus on comfort care and adequate sedation in an appropriate medical facility 1
• There are currently no known effective rabies antiviral drugs 3