Bah
yersinia pestis might be treatable with antibiotics, but it's still nasty. Bubonic Plague not so much (that's the "skin infection" variety -- 72 hours and 50% mortality if untreated), but certainly Pneumonic Plague (inhaled). Time from exposure to completion is 24 hours, with a 90 percent mortality rate. And it's highly contagious. Think of Anthrax that works faster and is easier to deliver (Anthrax is used as a weapon in part because it isn't contagious, so you can localize the effect -- an important consideration in warfare, but not as critical in terrorism). Sure, you can apply antibiotics if you catch it early enough, and if you have enough antibiotics in a region but the game is killing people before it's detected, and concentrating incidents to exceed the supply of antibiotics.
So for anthrax, killing a lot of people means weaponizing it and spraying it in crowded areas (not sending it through the mail). For yp, killing a lot of people means exposing a single person to the airborne form immediately before boarding a transpacific flight to a major US hub airport. By the time an outbreak is detected, thousands are already dead.
As for Iraq and Anthrax, I don't buy it. Sorry, the republicans have been looking for an excuse to go militarily after Iraq ever since Bush found himself lacking the testes to drive to Baghdad. Iraq could be behind it, but nothing concrete I've seen so far suggests that we're up against a particularly sophisticated germ warrior.