Thanks for the helpful information. IF we look at all the possible WMDs to be used by terrorist, the biological weapon remains, the cheapest, and technically, probably the easiest to deliver. The sustained effect of releasing an infectious agent on the human or livestock (ie food animal) population would be much easier and perhaps just as devastating.
Most bioweapons make for poor weapons of war. Anthrax, for instance, has had a vaccine available for it since Louis Pastuer invented it in 1859...and modern prescription anti-biotics defeat anthrax in all but the final stage.
Look for the terrorists to do more of what they do...which is to send idiot 12 year olds into night clubs, trains, and busses to each detonate 12 pounds of Semex.
They'll get an occasional sniper, and in some places they can even make car bombs.
If a state sponsor decides to use them, then they may knock off a single large-scale attack with something more potent. I'd bet money that Iraq under Hussein or Syria under Assad was the source for the terrorists' post-9/11 anthrax mailings, for instance (and that killed all of two people).
For perspective, the U.S. loses roughly 80 people per day in typical car wrecks.