Transmission

Transmission of the virus is through

• bite or scratch from an infected animal, usually dogs, but also cats, bats and other wildlife
• body fluids from an infectious animal coming into contact with an individual’s mucous membranes.
  • has a low probability of infection but must be managed as a significant event.
• transplantation of tissues or organs from someone who died from rabies
  • virus is present in some tissues and fluids of humans with rabies, but person-to-person spread of the disease has not been documented outside of transplantation
  • cases have occurred rarely outside the UK through corneal grafts and other transplanted tissues taken from individuals with rabies (1,2)

Infection does not occur through intact skin. Risk of introduction of virus into body increases form lick to scratch through to bite. Bites to the face are at highest risk (2)

Incubation period depends upon the size of the inoculum and the distance of the inoculum from the victim’s central nervous system but is generally between three and 12 weeks, but may range from four days to 19 years

• in more than 93% of patients, the onset is within one year of exposure (1)

Once the virus has entered the body it replicates in muscle cells near the entry wound. Virions penetrate nerve endings and travel in the axoplasm to the spinal cord and brain. When in the central nervous system the viruses again replicate before they spread to the salivary glands, lungs, kidneys and other organs via the autonomic nerves.

Reference:

• (1) Immunisation Against Infectious Disease - "The Green Book".Chapter 27 Rabies (November 2012)
• (2) Crowcroft NS, Thampi N.The prevention and management of rabies. BMJ. 2015;350:g7827.