Clinical manifestations of Rabies

· Virology

Five general stages of rabies are recognized in humans:

a) Incubation

b) Prodrome

c) Acute neurologic period

d) Coma and

e) Death (or, very rarely, recovery).


Incubation period in humans is usually 1-3 months but ranging from as few as 5 days to longer than 2 years after initial exposure, is more variable than in any other acute infection. Incubation periods may be somewhat shorter in children than in adults. The incubation period is usually short in individuals bitten close to the central nervous system such as face or head and long in those bitten in legs. This may be related to the distance virus has to travel to reach the brain.



Clinical symptoms are first noted during the prodromal period, which usually lasts from 2 to 10 days. These symptoms are often nonspecific (general malaise, fever, and fatigue) or suggests involvement of the respiratory system (sore throat, cough, and dyspnea), gastrointestinal system (anorexia, dysphagia, nausea, vomiting, abdominal pain, and diarrhea), or central nervous systems (headache, vertigo, anxiety, apprehension, irritability, and nervousness). More remarkable abnormalities (agitation, photophobia, priapism, increased libido, insomnia, nightmares, and depression) may also occur, suggesting encephalitis or psychiatric disturbances. Pain or paresthesia at the site of virus inoculation, combined with a history of recent animal bite, should suggest a consideration of rabies.

Acute neurologic period

The acute neurologic period begins with objective signs of central nervous system dysfunction. The disease may be classified as furious rabies if hyperactivity (i.e., hydrophobia) predominates and as dumb rabies if paralysis dominates the clinical picture. Fever, paresthesia, nuchal rigidity, muscle fasciculations, focal and generalized convulsions, hyperventilation, and hypersalivation may occur in both forms of the disease. Hydrophobia is characterized by difficulty in drinking together with intense thirst. Patient may be able to swallow dry solids but not liquids. Attempts to drink bring painful spasm of pharynx and larynx producing choking or gagging that patient develops a fear of even sight or sound of water. Coma and Death At the end of the acute neurologic phase, periods of rapid, irregular breathing may begin; paralysis and coma soon follow. Respiratory arrest may occur thereafter, unless the patient is receiving ventilatory assistance, which may prolong survival for days, weeks, or longer, with death due to other complications. Although life support measures can prolong the clinical course of rabies, rarely will they affect the outcome of disease. The possibility of recovery, however, must be recognized, and when resources permit, every effort should be made to support the patient. Seven cases of human “recovery” have been documented.

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