Smallpox was one of humanity's greatest
but a Worldwide Eradication Effort has eliminated it
from the human population.
Only a few samples are known to exist,
and these may be destroyed soon.
Smallpox fears now focus on its
deliberate reintroduction (bioterrorism)
a lab accident, or on the discovery of a smallpox reservoir.
There is some evidence that the virus
can remain viable for years or even decades.
Medicine could eradicate smallpox because
it has one stable strain and no animal reservoir,
making it vulnerable to a concerted program
of prevention by vaccination.
Once a person has contracted the illness, however,
there is no known remedy. Historically, mortality in populations
with no natural immunity to the disease runs 90% or more.