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Key Features

  • A rhabdovirus infection causing encephalitis, transmitted by infected saliva after an animal bite

  • Bats, raccoons, and skunks are most common vectors in the United States

  • Other rabid animals include foxes, cats, cattle, and dogs

  • Human cases rare in the United States

  • Incubation period of 3–7 weeks, proportional to distance from wound to CNS

  • Usually fatal unless patients receive postexposure prophylaxis

Clinical Findings

  • Prodrome includes pain at site of bite, fever, nausea

  • CNS symptoms (encephalitis or paralysis) begin about 10 days later

  • Encephalitis: delirium and extremely painful laryngeal spasms that lead to hydrophobia

  • Paralysis: less common; ascending paralysis resembles Guillain-Barré syndrome

  • Both encephalitic and paralytic forms progress to coma, autonomic dysfunction, death

Diagnosis

  • Diagnosis suggested by history of animal bite, initial viral prodrome followed by CNS symptoms

  • Diagnosis confirmed with fluorescent antibody testing of sacrificed animal brain

  • Skin biopsy from the patient's posterior neck has ~80% sensitivity

  • Quantitative reverse transcriptase PCR (qRT-PCR), nucleic acid sequence-based amplification, direct rapid immunohistochemical test (DRIT) and viral isolation from the cerebrospinal fluid or saliva are advocated as definitive diagnostic assays

Treatment

  • Animal bite wounds should not be sutured

  • Local wound cleansing, débridement, and flushes are useful

  • Treatment includes both passive antibody and vaccination

  • Single case report of treatment success with ribavirin, amantadine, plus midazolam

  • A combination of rabies vaccine, rabies immune globulin, monoclonal antibodies (investigational), ribavirin, interferon-α, and amantadine may be helpful

  • For suspected cases, use of postexposure immunization should be based on clinical guidelines, and on recommendations of local health officials

  • Prevention

    • Immunization of household dogs

    • Avoidance of animals associated with rabies

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