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Rabies Virus

Rabies virus

For medical students2 min readUpdated 2026-10-10

Rabies virus is a zoonotic RNA virus belonging to the family Rhabdoviridae, causing a fatal infectious disease of the nervous system known as hydrophobia (rabies). The pathogen is transmitted through a bite or saliva contamination of a wound by an infected animal and targets neurons of the central nervous system.

FamilyRhabdoviridae
TargetCNS Neurons
GenomeSingle-stranded linear negative-sense RNA
PrognosisFatal

Taxonomy and Virion Structure

The rabies virus belongs to the family Rhabdoviridae, genus Lyssavirus. This genus also includes related bat viruses (e.g., Lagos bat, Mokola, and Duvenhage viruses) that share a similar morphology with the classic pathogen and are isolated primarily in Africa.

The virion has a characteristic bullet-like shape, with dimensions ranging from 75 to 180 nm. Its internal structure includes:

Genome and Proteins: The genetic material is represented by a single-stranded linear negative-sense RNA. Associated with it is the nucleoprotein (N protein), which forms the capsid. Beneath the lipoprotein envelope lies the matrix protein M. Surface spikes consist of glycoprotein G. Additionally, the virus contains a polymerase complex, including a large L protein and a phosphoprotein P (or NS), which are responsible for viral RNA synthesis.

Antigenic Properties and Immune Response

The main antigen of the rabies virus is glycoprotein G. It forms the surface spikes of the virion and performs crucial functions:

In response to viral invasion, the body produces specific virus-neutralizing antibodies directed precisely against glycoprotein G. These antibodies can be detected using a neutralization test.

Internal proteins (ribonucleocapsid) act as group-specific antigens. To detect viral antigens, the direct fluorescent antibody (DFA) test, complement fixation test (CFT), and precipitation test are used.

Life Cycle (Replication)

The replication process of the rabies virus occurs in the cell cytoplasm and includes several stages:

  1. Adsorption and Penetration: The virus binds via glycoproteins to cellular receptors and enters the cell through clathrin-mediated endocytosis.
  2. Uncoating: Viral uncoating occurs within endosomes, after which the ribonucleocapsid is released into the cytoplasm.
  3. Biosynthesis (Transcription and Replication): Viral RNA-dependent RNA polymerase synthesizes short positive-sense strands (mRNA) for protein translation and full-length positive-sense strands that serve as templates to create new genomic negative-sense RNAs.
  4. Translation and Processing: Viral proteins are synthesized on cellular ribosomes. Glycoprotein G undergoes complex modification in the endoplasmic reticulum and Golgi apparatus before being inserted into the cell membrane.
  5. Assembly and Release: New copies of negative-sense RNA bind with proteins to form the ribonucleocapsid. Mature virions exit the cell via budding through membrane areas containing viral glycoproteins.

Variants and Diagnostics

Two variants of the rabies virus are distinguished; they are identical in antigenic structure but differ in biological properties:

Intracerebral inoculation of laboratory animals or cell cultures is used to cultivate the virus. A key diagnostic feature of the street virus is the formation of specific eosinophilic cytoplasmic inclusions in brain neurons — Negri bodies (1–15 µm in size), which consist of viral ribonucleoprotein.

Pathogens are rapidly inactivated by UV irradiation, heating (above 60 °C), alkalis, lipid solvents, and proteolytic enzymes, but they survive well at low temperatures (–20 °C to –70 °C).

Frequently asked questions

Through which neural pathways does the rabies virus spread from the bite site to the CNS?

The rabies virus spreads from the bite site to the central nervous system via axons of peripheral nerves. Following primary replication at the portal of entry, the pathogen invades motor or sensory neurons. Subsequent centripetal movement to the brain and spinal cord occurs via retrograde axonal transport along neural pathways. Upon reaching the CNS, the virus actively replicates in neurons of the medulla oblongata, hippocampus, and other structures, after which centrifugal dissemination to the periphery begins.

Which animals are the primary reservoirs of the wild rabies virus in nature?

The primary reservoirs of the wild rabies virus in natural foci include wild carnivores, rodents, and bats.

  • Carnivores — red foxes, wolves, raccoon dogs, arctic foxes, jackals, corsac foxes, badgers, skunks, and mongooses. They act as the main vectors of infection.
  • Small mammals — rodents (mice, rats), hedgehogs. They comprise the prey base for carnivores and help sustain natural reservoirs.
  • Bats — including vampire bats, which also serve as primary reservoirs for other Lyssavirus species.
Through what routes can the rabies virus be transmitted to humans?

Rabies virus is transmitted to humans primarily via contact, though other routes of infection are possible.

  • Contact route (primary) — occurs via virus-contaminated saliva from infected animals through bites, as well as contamination of broken skin (microabrasions), conjunctiva, and intact mucous membranes.
  • Aerosol route — possible under specific conditions, such as exploring caves inhabited by infected bat colonies or in laboratory settings.
  • Alimentary route — a rare variant occurring upon consumption of meat from infected animals.
  • Transplantation route — transmission via transplantation of infected tissues (e.g., corneas).

Transplacental transmission is also a theoretical possibility.

What does specific post-exposure prophylaxis for rabies entail?

Specific post-exposure prophylaxis for rabies is performed to rapidly build immunity before the virus reaches the CNS and includes local wound care, vaccination, and, in severe exposures, passive immunization. Rabies vaccine is administered intramuscularly according to a scheduled regimen following exposure. For multiple or deep wounds, as well as bites in high-risk areas (face, head, neck, hands), rabies immunoglobulin (RIG) is additionally administered on day zero. A combined course is also indicated for injuries inflicted by wild or farm animals.

What is the shape of the rabies virion?

Rhabdoviruses have a characteristic bullet-like virion shape measuring 75–180 nm.

Which antigen is responsible for inducing virus-neutralizing antibodies?

The surface glycoprotein G (supercapsid spikes) is responsible for inducing virus-neutralizing antibodies.

What are Negri bodies?

These are specific eosinophilic cytoplasmic inclusions found in neurons, composed of viral ribonucleoprotein. They serve as a key diagnostic marker for street rabies.

What is the difference between street virus and fixed virus?

Street virus circulates in nature and is highly pathogenic. Fixed virus is artificially derived (by L. Pasteur), safe for humans, does not form Negri bodies, and is used for vaccine production.

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