http://www.iraqwatch.org/wmd/biological.html
"Smallpox: The virus can be inhaled or absorbed by the skin. Its initial symptoms are like a severe flu, then a rash appears. Smallpox kills about a third of unvaccinated victims, but the vaccine is highly effective. The virus can be stored over long periods of time if it is freeze-dried, and it is easy to produce, making it a good candidate for biological warfare. In addition, countries like the United States are susceptible, as all natural occurrences of smallpox were eradicated by 1980, making regular vaccinations unnecessary. Iraq was reported in late 1998 to be suspected of concealing the smallpox virus, but this has not been confirmed."
Here is a discussion about Iraqi smallpox with an expert from Sandia Labs.