Smallpox symptoms develop about 12 days after exposure. The disease usually is not contagious until the rash first appears. As scabs form, the chance of passing on the disease decreases.
Smallpox was a worldwide problem in the past. But because of a widespread vaccination program, it was declared eradicated (no longer a naturally occurring disease) by the World Health Organization (WHO) in 1980.
There may be a risk that the smallpox virus could be manufactured by people in order to threaten or harm others.
eMedicineHealth Medical Reference from Healthwise
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