Description

• A rapidly progressive central nervous system (CNS) infection caused by RNA rhabdovirus affecting humans and mammals
• May present with symptoms of encephalitis or paralysis
• Generally considered 100% fatal after symptoms onset
• Vaccine-preventable
• System(s) affected: CNS
• Synonym(s): hydrophobia (inability to swallow water)

Epidemiology

• Present on all continents except Australia and Antarctica
• >95% of human deaths related to rabies occur in Asia and Africa.
• Bats are the most common reservoir in the United States.
• Dogs are the most common reservoir worldwide.

Incidence

• Estimated 55,000 deaths worldwide per year
• Typically only 1 to 3 cases per year in the United States: 1/3 of those exposures occur outside of the United States

Etiology and Pathophysiology

• Family Rhabdoviridae; genus Lyssavirus: bullet-shaped enveloped, negative-sense single-stranded RNA, neurotropic virus
• Transmission occurs from a bite by an infected animal or when the saliva of an infected animal comes into contact with an open wound or mucous membrane.
  • 60% of human cases of bat-variant virus in North America report no history of bat bite or scratch and 33% report no history of bat contact.
  • Although rare, there are reported cases of laboratory aerosolization and infection from transplanted organs.
• Following transmission, the virus replicates within the muscle and binds to acetylcholine receptors located at the neuromuscular junction.
  • The virus travels retrograde through nerves to the CNS where infection of the dorsal ganglia leads to pain. Viral replication in the brain can disseminate to other organs, including the salivary glands where it can be shed.

Risk Factors

• Professions or activities with exposure to infected animals (e.g., animal handlers, lab workers, veterinarians, cave explorers)
• Travel to countries where canine rabies is endemic.
• In the United States, most cases are associated with bat exposure.
• Internationally, exposure occurs through both domestic and feral dogs.
• There are reports of human-to-human transmission through cornea, solid organ, and other tissue transplants.

General Prevention

• Preexposure vaccination
  • For high-risk groups (veterinarians, animal handlers, wildlife rangers, and certain laboratory workers)
  • Consider preexposure vaccination for travelers to parts of the world with increased risk of rabies from domestic animals (i.e., North Africa).
• Source control and avoidance
  • Immunization of dogs and cats has led to a dramatic decrease in U.S. cases since the 1950s.
  • Contact animal control and avoid approaching or handling wild (or domestic) animals exhibiting strange behaviors.
• Postexposure prophylaxis
  • Seek treatment promptly if bitten, scratched, or in contact with saliva from potentially infected animal.
  • Prevent infection by prompt postexposure treatment.
  • Consider postexposure prophylaxis for individuals in direct contact with bats.
  • Hospital contacts of patients infected with rabies do not require postexposure prophylaxis unless there has been exposure through mucous membranes or an open wound (including a bite) to saliva, cerebrospinal fluid (CSF), or brain tissue from the infected patient.
  • Hospitalized patients should be placed in contact isolation with gowns, gloves, goggles, and masks.