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Species of the month

Smallpox Virus

Some facts about this virus:

Description:
Smallpox was an infectious disease caused by one of two virus variants, Variola major and Variola minor. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) certified the global eradication of the disease in 1980. Smallpox is one of two infectious diseases to have been eradicated, the other being rinderpest in 2011. Status: Eradicated.
Vernacular Names - The term "smallpox" was first used in Britain in the early 16th century to distinguish the disease from syphilis, which was then known as the "great pox". Other historical names for the disease include pox, speckled monster, and red plague.

The date of the appearance of smallpox is not settled. It most likely evolved from a terrestrial African rodent virus between 68,000 and 16,000 years ago. 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 (kbp) in size and containing a hairpin loop at each end. The two classic varieties of smallpox are variola major and variola minor. Transmission occurred through inhalation of airborne Variola virus, usually droplets expressed from the oral, nasal, or pharyngeal mucosa of an infected person.

It was transmitted from one person to another primarily through prolonged face-to-face contact with an infected person, usually within a distance of 1.8 m (6 feet), but could also be spread through direct contact with infected bodily fluids or contaminated objects (fomites) such as bedding or clothing. The mortality rate from variola minor is approximately 1%, while the mortality rate from variola major is approximately 30%. The global eradication of smallpox was certified, based on intense verification activities, by a commission of eminent scientists on 9 December 1979 and subsequently endorsed by the World Health Assembly on 8 May 1980.