Anthrax. The very name of this biological agent sounds menacing - which should not be surprising, as it is derived from an ancient Greek word meaning "burning coal."
It is indeed one of the most dangerous mass-destruction weapons of the post-cold-war era. Many security officials believe that the US may now need to fight the spread of anthrax and other biological threats as intensely as it has long opposed the proliferation of nuclear warheads.
But anthrax is far from a perfect terrorist tool, and it is not yet clear that even Iraqi leader Saddam Hussein has acquired more than crude biological weapons, say experts. To call anthrax the "poor man's atom bomb" may be to overstate the case - for now.
"The thing about it is that it is very easy to produce, but it is very difficult to deliver effectively," says Jonathan Tucker, director of the chemical and biological weapons nonproliferation project at the Monterey Institute of International Studies in California.
Last week's arrest of two men in Las Vegas thought to be carrying anthrax could be seen as a wake-up call for domestic law-enforcement agencies. The substance in question turned out to be a harmless version of the anthrax bacteria used as a vaccine, but many experts worry that the next Timothy McVeigh may use biological substances instead of explosives - since raw materials of such agents are not that difficult to obtain.
Iraq, for instance, has admitted producing huge amounts of the anthrax agent. Of the three categories of weapons of mass destruction - nuclear, chemical, and biological - many experts now judge biological to be the greatest threat to the world. That's because they have greater potential than chemical weapons for widespread destruction, and they also represent a technology more widespread than nuclear science.
When it comes to terror weapons, "biological weapons should now be the most serious concern," writes Columbia University political science professor Richard Betts in a recent article in the journal Foreign Affairs. He points out that one plane spraying 100 kilograms of anthrax over Washington on a clear, calm night could produce between 1 million and 3 million casualties, according to a Congressional Office of Technology Assessment (OTA) report. That's 300 times the damage that a similar attack with sarin nerve gas would cause.
But "availability" in this case is a relative term. While the raw materials of biological weapons can be easy to get, it is not so easy to turn that material into a usable, dangerous weapon.
Consider the case of the Japanese cult Aum Shinrikyo, which carried out a deadly chemical nerve gas attack on a Tokyo subway in 1995. Two years before switching to chemicals, members of the cult had brewed anthrax and botulinum toxin in their own microbiological facility. They repeatedly released anthrax spores from the roof of a Tokyo high-rise in 1993. Technical problems rendered these attacks ineffective. They produced little but an offensive odor.
A wet slurry of anthrax biological agent can be easily grown in equipment used to produce innocent antibiotics, cattle-feed supplements, or even yogurt or beer. The agent is most dangerous, however, if dried and then ground into spores of a particular size. Accomplishing this is both difficult and dangerous to anyone trying it, experts point out.
"It's technically challenging to produce dried anthrax," says Jonathan Tucker of the Monterey Institute. "Iraq was working on it, but they still had only wet slurries at the time of the Gulf War."
Whether Iraq has since made the leap to a dried form of the weapon is just the sort of thing United Nations weapons inspectors try to track. As yet they have turned up no definitive evidence of such a capability, or at least they have not publicly discussed any such evidence.
The sheer amount of biological agent produced by Iraq remains daunting. According to a recent US government report, Iraq's biological weapons program produced 22,457 gallons of anthrax and 100,393 gallons of botulinum toxin.
But the bombs and missiles Iraq had stockpiled to deliver biological agents were mostly crude models. Experts say they would have been unable to deliver anthrax or botulinum with any sort of deadly efficiency.
That's because the Iraqi military did not have the right kind of fuses.
Optimum dispersal of agent requires that a munition explode just before impact, via what's known as a "proximity fuse." Such a fuse senses the nearness of an object - in this case the earth - and explodes accordingly.
Iraqi Scuds were outfitted with easier-to-produce contact fuses, however. That means warheads would explode on contact, with much biological agent simply being absorbed in the ground.
"If they had tried to use a bio-warfare agent in their Scuds, chances are that only about 5 percent of the payload would have been properly disseminated," says Kenneth Pollack, a military expert at the Washington Institute for Near East Policy.
Such an attack would still be a tragedy capable of causing hundreds of casualties. But it would be far from the scenario of millions dead painted by the OTA report, which assumed technically optimal agent, weather, and method of dispersal.