MICROBIOLOGY

• Rabies is caused by an enveloped, single-stranded, negative-sense RNA virus in the genus Lyssavirus (family Rhabdoviridae) and nearly always causes fatal encephalitis in humans and other mammals.
  
  • Classic rabies virus is the predominant human pathogen globally, but other Lyssavirus species, including European bat lyssaviruses, also cause human rabies.
  • The virus is highly neurotropic, entering peripheral nerves at the inoculation site and spreading centripetally to the CNS via retrograde axonal transport.
    • Typical exposures involve infected saliva or neural tissue contacting broken skin or mucous membranes; transmission also occurs through infected organ or tissue transplantation.
      • Blood, urine, and feces are not considered rabies exposures.
• The domestic dog is the main reservoir worldwide.
  • Wildlife species predominate in the U.S.
    • Major U.S. wildlife reservoirs include bats, raccoons, skunks, and foxes; their importance varies geographically.
      • Hawaii is rabies-free; otherwise, all other states in the U.S. are at risk.
• Transmission usually occurs when virus-laden saliva is inoculated through a bite; viral replication in salivary glands facilitates transmission.