Rabies
Rabies is a bullet-shaped rhabdovirus transmitted by bat, raccoon, skunk, or dog bites that causes a uniformly fatal encephalomyelitis once symptoms begin, marked by hydrophobia and aerophobia. Prevention is everything: thorough wound washing plus rabies immune globulin and vaccine given before symptom onset prevents disease, but there is no effective treatment after clinical rabies develops.
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What this article covers
- Overview
A bullet-shaped rhabdovirus causing fatal encephalomyelitis: rabies virus travels along peripheral nerves to the central nervous system after inoculation, most often through an animal bite, and once…
- Epidemiology
Rare in the United States: only 1 or 2 human rabies cases are reported annually in the United States, reflecting the success of postexposure prophylaxis and animal vaccination programs.
- Risk factors
Bite or scratch from a bat, raccoon, skunk, fox, or unvaccinated dog: the principal mechanism of exposure; aerosol transmission (for example in bat caves) is also possible without a bite.
- Pathophysiology
Retrograde axonal transport to the central nervous system: after inoculation into muscle or subcutaneous tissue, the virus replicates locally, then travels by retrograde transport along peripheral…
- Clinical features
Rabies should be considered in any case of unexplained encephalitis or myelitis, especially with a history of an animal bite or travel outside the United States, since a strong index of suspicion is required for antemortem diagnosis.
- Differential diagnosis
Herpes simplex virus encephalitis: overlapping presentation of fever, altered mentation, and CNS findings; discriminated by temporal lobe changes on MRI and HSV PCR of cerebrospinal fluid, and by the absence of a bite exposure history.
- Diagnosis
A confirmed antemortem diagnosis requires a strong index of clinical suspicion, because no single bedside test is rapid or fully sensitive early in illness; the disease is confirmed by a combination…
- Management
Once symptomatic disease is established, there is no effective treatment for rabies; care is supportive and focused on comfort, and the disease is essentially universally fatal.
- Complications
Progressive encephalomyelitis with respiratory failure and death: the near-universal outcome once clinical rabies develops.
- Prognosis
Once clinical symptoms of rabies appear, the disease is essentially universally fatal, with exceedingly rare survival even with maximal supportive intensive care.
- Prevention
Immediate, thorough wound washing with soap and water after any animal bite is the single most effective, low-cost preventive step and should never be delayed pending a prophylaxis decision.
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- Herpes simplex virus (HSV) infection
Herpes simplex virus type 1 or 2 establishes lifelong latency in sensory ganglia after mucocutaneous infection, causing painful vesicular-to-ulcerative outbreaks of the mouth or genitals with intermittent asymptomatic shedding; diagnosis is by NAAT of an ulcer swab and treatment is oral nucleoside analogues, escalating to intravenous acyclovir for encephalitis, severe mucocutaneous disease, or disseminated infection in immunosuppressed hosts.
- Bacterial meningitis (age over 1 month)
Acute purulent infection of the meninges beyond the neonatal period, most often from Streptococcus pneumoniae or Neisseria meningitidis, diagnosed by CSF analysis after prompt lumbar puncture and treated with immediate empiric intravenous antibiotics plus adjunctive dexamethasone, since any delay in therapy worsens outcome and mortality remains near 25%.
- Vaccines
Vaccines are live attenuated, inactivated, subunit, conjugate, or toxoid preparations that induce antigen-specific active immunity to prevent infection or its complications before exposure occurs. Selection follows the age- and risk-based Advisory Committee on Immunization Practices schedule, with routine adult boosting such as Tdap every 10 years, and inactivated regimens substituted whenever a live vaccine is contraindicated by pregnancy or immunosuppression.
- Isolation precautions
Isolation precautions pair standard precautions, used for every patient, with transmission-based precautions selected by a suspected or confirmed organism's dominant route: contact (gloves and gown), droplet (mask within 3 to 6 feet), or airborne (a negative-pressure room and a fit-tested N95 respirator). Hand hygiene and matching the barrier to the route are the core interventions.