This segment on Wisconsin Public Radio's "To The Best of Our Knowledge," gives the best (if pretty gloomy) expert view of our risks with respect to bio-weapons. Forget about plastic sheeting and duct tape -- they're useless. Depend entirely on our intelligence agencies (!) and our public health system (!!). Okay, so both stink. Okay, pray, I guess.
"Raymond Zilinskas directs the Chemical and Biological Weapons Nonproliferation Program at the Monterey Institute of International Studies. He was a UN weapons inspector in Iraq. Zilinskas tells Jim Fleming that a biological weapon is live organism while a chemical weapon uses an inert substance. He says the best response is a good public health system."
http://www.wpr.org/book/030302b.html and
http://www.wpr.org/book/realaud.html for listening online when the audio becomes available, shortly.