Smallpox
Smallpox is a highly contagious disease unique to humans. It is estimated that no more than 20 percent of the population has any immunity from previous vaccination.
Smallpox outbreaks have occurred from time to time for thousands of years, but in 1980 the disease was declared eradicated following worldwide vaccination programs. Except for stockpiles in high-security laboratories, the virus has been eliminated. However, if obtained and deliberately released as a bioweapon, smallpox could cause a public health catastrophe.
Generally, direct and fairly prolonged face-to-face contact is required to spread smallpox from one person to another. Smallpox also can be spread through direct contact with infected bodily fluids or contaminated objects such as bedding or clothing. Rarely, smallpox has been spread by virus carried in the air in enclosed settings such as buildings, buses, and trains. Humans are the only natural hosts of variola. Smallpox is not known to be transmitted by insects or animals.
A person with smallpox is sometimes contagious with onset of fever (prodrome phase), but the person becomes most contagious with the onset of rash. At this stage the infected person is usually very sick and not able to move around in the community. The infected person is contagious until the last smallpox scab falls off.
Vaccination within 3 days of exposure will completely prevent or significantly modify smallpox in the vast majority of people. Vaccination 4 to 7 days after exposure likely offers some protection from disease or may modify the severity of disease.
For more information on Smallpox, see OSHA's Smallpox Webpage.
Knowledge Check Choose the best answer for the question.
5-9. Which of the following has been eradicated but could cause a public-health catastrophe if deliberately released as a bioweapon?
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