[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Other DNA viruses](https://durgical.com/en/microbiology/groups/other-dna-viruses/) › Variola virus

[Microbiology](https://durgical.com/en/microbiology/) · [Other DNA viruses](https://durgical.com/en/microbiology/groups/other-dna-viruses/)

# Variola virus

- Virus
- Enveloped
- Contact
- Airborne
- For completeness

The poxvirus of smallpox, a disease eradicated in 1980 thanks to vaccination; it now exists only in authorized laboratories.

Updated 2026-11-01

Also called: smallpox, variola

## Key points

- Eradicated: last natural case in 1977 and eradication declared in 1980.
- Synchronous, centrifugal lesions (palms and soles); chickenpox is asynchronous and centripetal.
- Airborne and contact precautions.
- The vaccine uses vaccinia, another orthopoxvirus, not variola itself.

## At a glance

**Shape**
Large, brick-shaped, enveloped

**Genome**
Linear double-stranded DNA

**Envelope**
Enveloped

**Family**
Poxviridae (genus Orthopoxvirus)

**Size**
About 300 nm

## Morphology

- Large brick-shaped virus
- Cytoplasmic replication with inclusion bodies (Guarnieri bodies)

## Transmission

- Prolonged face-to-face contact (respiratory droplets and aerosols)
- Contact with lesions, clothing or contaminated bedding

**Reservoir:** Humans only: that is why it could be eradicated

### Isolation precautions

What the care team adds to standard precautions.

**Contact**
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.

**Airborne**
N95 respirator and a negative-pressure room.

## Virulence factors

- Proteins that inhibit complement and interferon
- Considered a high-priority bioterrorism agent

## Diseases it causes

- Smallpox

## Clinical picture

- Incubation of 7 to 19 days, with no contagiousness during that time
- High fever and prostration, then a rash in the mouth and face that spreads to the limbs, palms and soles (centrifugal)
- All lesions in one area are at the same stage: macule, papule, vesicle, pustule and crust
- Severe forms: flat (malignant) and hemorrhagic

## Diagnosis

- A single case would be a public health emergency: immediate notification
- PCR in high-containment reference laboratories

## Treatment

There have been no natural cases since 1977. Antivirals such as tecovirimat are stockpiled for emergencies, along with supportive care.

Drug class only; doses and regimens are set by the clinician from the current guideline.

## Prevention

- Live vaccinia virus vaccine, which protects if given before or soon after exposure
- Airborne and contact precautions until all scabs have fallen off

**Vaccine:** The vaccinia vaccine (given with a bifurcated needle) made eradication possible; it is no longer given to the general public.

## Memory aid

Smallpox marches in a parade, every lesion in step; chickenpox turns up as an unruly crowd.

## Test yourself

Think of the answer, then tap the question to see it.

## In which year was smallpox declared eradicated?

In 1980, by the World Health Assembly; the last natural case was in 1977.

## Which virus does the smallpox vaccine contain?

Vaccinia virus, a related orthopoxvirus that does not cause smallpox.

## Which isolation precautions would a smallpox case require?

Standard, airborne and contact precautions for the whole illness, until the scabs have fallen off.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/microbiology/variola-virus/)

## Related

- [Mpox virus](https://durgical.com/en/microbiology/mpox-virus/)
- [Varicella-zoster virus](https://durgical.com/en/microbiology/varicella-zoster-virus/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

**Contact**
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.

**Droplet**
Surgical mask within about a metre; single room.

**Airborne**
N95 respirator and a negative-pressure room.

[← Back to the group: Other DNA viruses](https://durgical.com/en/microbiology/groups/other-dna-viruses/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Clinical Signs and Symptoms of Smallpox](https://www.cdc.gov/smallpox/hcp/clinical-signs/index.html) (CDC, 2024); [About Smallpox](https://www.cdc.gov/smallpox/about/index.html) (CDC, 2024); [Smallpox Vaccine](https://www.cdc.gov/smallpox/vaccines/index.html) (CDC, 2024); [Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions](https://www.cdc.gov/infection-control/hcp/isolation-precautions/appendix-a-type-duration.html) (CDC, 2024).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/microbiology/variola-virus/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/variola-virus/