# Rabies Virus

> Rabies virus for MBBS Microbiology: bullet-shaped rhabdovirus, Negri bodies, categories of exposure, wound washing, post-exposure prophylaxis and vaccines.

- Canonical URL: https://prepelephant.com/topics/mbbs/microbiology/rabies-virus
- Exam / course: MBBS · Subject: Microbiology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Rabies Virus", PrepElephant, https://prepelephant.com/topics/mbbs/microbiology/rabies-virus

## Direct answer

Rabies virus is a bullet-shaped, enveloped, negative-sense single-stranded ribonucleic acid rhabdovirus of the genus Lyssavirus, transmitted in saliva through bites of rabid animals, overwhelmingly dogs in India. It travels retrograde along peripheral nerves to the central nervous system, producing furious or paralytic rabies, and is virtually always fatal once symptoms begin — so prevention after exposure is everything: wound washing, vaccination and, for category three exposures, immunoglobulin. Negri bodies in neurons are the pathological hallmark.

## What you must remember

- **Structure and pathology:** bullet-shaped virion with glycoprotein projections; diagnosis in animals is by the direct fluorescent antibody test on brain smears, with Negri bodies in hippocampal and Purkinje neurons as the classical finding, though they may be absent.
- **Pathogenesis:** virus replicates in muscle, binds nicotinic acetylcholine receptors at the neuromuscular junction and ascends axons to the brain, then spreads to salivary glands, cornea and skin; incubation is one to three months, shorter after face and hand bites.
- **Clinical forms:** furious rabies with hydrophobia, aerophobia, agitation, hypersalivation and painful swallowing spasms, and the paralytic or dumb form with ascending flaccid paralysis; both are fatal.
- **Categories of exposure:** category one, touching or licks on intact skin, needs nothing; category two, nibbling or minor scratches without bleeding, needs vaccine; category three, transdermal bites or scratches and licks on broken skin or mucosa, needs vaccine plus rabies immunoglobulin.
- **Wound care:** wash with soap and running water for fifteen minutes, apply povidone-iodine, and avoid primary suturing where possible — the most beneficial first step, equal to any vaccine.
- **Vaccines:** modern cell-culture vaccines given intramuscularly or by updated intradermal regimens; immunoglobulin is infiltrated into and around the wound, the rest given at a distant site; pre-exposure vaccination protects animal handlers.
- **Human diagnosis:** ante-mortem polymerase chain reaction of saliva, nuchal skin biopsy and corneal impressions; post-mortem brain examination with the fluorescent antibody test.

## Common confusion

Local wound toilet is the single most beneficial measure, removing virus at the portal of entry. The exposure categories are memorised wrongly — a lick on broken skin is category three, needing immunoglobulin, while a lick on intact skin needs nothing. Immunoglobulin is given only once, infiltrated into the wound, never into the same syringe or site as vaccine.

## Exam-focused takeaway

In theory, describe the virus, pathogenesis with the reason for variable incubation, Negri bodies, the exposure categories with their prophylaxis, and the vaccine regimens. In viva, expect what to do for a bite on the face, why incubation varies and where Negri bodies are found. At the practical, charting post-exposure prophylaxis for a category three dog bite is the standard exercise.

## Frequently asked questions

### What are Negri bodies?

Eosinophilic cytoplasmic inclusions in hippocampal pyramidal and cerebellar Purkinje cells — pathognomonic but not always present, so the fluorescent antibody test is the reference standard.

### How are exposures categorised?

Category one licks on intact skin need nothing; category two nibbling or minor scratches without bleeding need vaccine; category three transdermal bites and licks on broken skin or mucosa need vaccine plus immunoglobulin.

### Why is wound washing emphasised?

Fifteen minutes of washing with soap and running water physically removes and inactivates virus at the wound — the most immediately available measure after any bite.

### Who needs pre-exposure vaccination?

Veterinarians, animal handlers, laboratory workers and dog catchers, vaccinated on days zero and seven; they still need boosters after exposure.

### Can rabies be treated once symptoms begin?

Practically no — it is almost invariably fatal, which is why prevention after exposure receives absolute priority.

### Which tests diagnose rabies in humans?

Ante-mortem polymerase chain reaction on saliva, nuchal skin biopsy with hair follicles and corneal impressions; post-mortem brain examination with the direct fluorescent antibody test.