An Overview of the Cause of Smallpox
The cause of
smallpox is an infection with the
variola virus. Variola virus is a double-stranded DNA virus in the family
Poxviridae and the genus
Orthopoxvirus. Variola virus only infects humans.
Thanks to the success of vaccination, the last natural outbreak of smallpox in the U.S. occurred in 1949. By 1972, routine smallpox vaccinations for children in the United States were no longer needed. In 1980, smallpox was said to be eliminated worldwide, and no cases of naturally occurring smallpox have happened since.
Because smallpox was wiped out many years ago, a case of smallpox today would be the result of an intentional act. A single confirmed case of smallpox would be considered an emergency.
Smallpox is highly contagious. In most cases,
smallpox transmission occurs by inhaling droplets of saliva, which are full of virus, during face-to-face contact with an infected person. In most cases, fairly prolonged face-to-face contact (3 or more hours) is required.
Occasionally, smallpox can be transmitted:
- Through direct contact with infected fluids or contaminated objects
- Through the air.
When the smallpox virus enters the body, it spreads within the bloodstream to small blood vessels in the skin. After 7-17 days,
smallpox symptoms will begin.
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