Variola

Variola is a genus of viruses in the family Poxviridae in the subfamily Chordopoxvirinae. The natural hosts are humans. Diseases associated with this genus include: smallpox. There are currently two recognized species in this genus including the type species Variola major. The second species is Variola minor.

History

The history of Variola is intertwined with the history of smallpox, a highly infectious and often-deadly disease that has affected humans for thousands of years. The World Health Organization (WHO) certified the eradication of smallpox in 1980. The last known natural case was in Somalia in 1977. Since then, the only known cases were caused by a laboratory accident in 1978 in Birmingham, England, which killed one person and caused a limited outbreak. Smallpox was officially declared eradicated in 1980.

Virology

Variola is a large brick-shaped virus measuring approximately 302 to 350 nanometers by 244 to 270 nm, with a single linear double stranded DNA genome 186 kilobase pairs in size. The two classic Variola species are Variola major and Variola minor. Variola major is the more deadly form, with a more severe rash and higher fever. Variola minor causes a milder form of disease and only rarely results in death.

Transmission

Variola is transmitted from person to person primarily through prolonged face-to-face contact with an infected person, usually within a distance of 6 feet (1.8 m), but can also be spread through direct contact with infected bodily fluids or contaminated objects (fomites) such as bedding or clothing.

Treatment and Prevention

There is no specific treatment for variola infection. Prevention is achieved through the smallpox vaccine. The vaccine is made from a virus called vaccinia, which is a poxvirus similar to variola but less harmful. The vaccine helps the body develop immunity to smallpox.

See Also

• Smallpox
• Poxviridae
• Vaccinia

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