About a week after September 11, someone began sending envelopes containing anthrax spores to members of the media, and the Microsoft corporation. One editor in Florida has died and several others around the nation are being treated. Anthrax is much more effective at terrorizing people than killing them. If you know you have anthrax early on, it can easily be treated with antibiotics. But if you don't know you have it, it quietly goes on and kills you. By the time you get symptoms, it's usually too late for treatment.
The current attacks appear to be the work of more than one person. Some of the attacks are bogus, with talcum powder (or something similar) being put into envelopes to make the recipient think they are receiving anthrax. If you can see anthrax spores at all, it's as a very fine dust. The stuff encountered in the recent attacks is natural anthrax, although of a strain long used in agricultural research. Anyone with access to a college agriculture department or research center could obtain anthrax spores. Finding them in the wild is difficult, unless you come across some animals who have recently died from it. Even then, you have to know how to extract the bacteria from the corpses, culture it and then turn the bacteria into spores. There are also bioengineered versions of anthrax out there for military use, but none of that has been encountered. Militarized anthrax varies in its characteristics; being either more lethal, resistant to antibiotics, or easier to spread in the air, or all of the above.
Anthrax is a bacteria that can thrive inside animals. Normally, anthrax exists as tiny spores. The spores tend to clump together. Individual spores cannot be seen with the naked eye. These spores can live for decades in soil, waiting for an animal to come along eating grass and, while doing that, breathe in or digest the spores. But the most common way to get anthrax is in the skin (cutaneous anthrax). If spores get into a cut or sore, there will be a swelling, but eventually the blister will go away. Antibiotics will eliminate any danger This form of anthrax attack is rarely fatal. Animals like sheep often have spores in their wool and cattle have it on their hides. Farmers and other workers (like veterinarians) who handle these animals get cutaneous anthrax often enough that many receive an anthrax vaccine. The vaccine makes it nearly impossible for anthrax to injure or kill a victim. But it's also common for people, and animals, exposed to anthrax regularly to catch non-lethal doses and develop natural immunity.
When the spores turn into bacteria and grow, a poison is given off. In an animal with a strong constitution, the anthrax bacteria will be destroyed. But if enough spores get into the body at one time, the person, or animal, dies. In the wild, the dead animals rot (or are eaten by scavengers, killing some of them with anthrax) and the anthrax bacteria turn to spores once more and waits for another host to come along. What makes an internal anthrax attack so deadly is that you don't get any symptoms (which resemble the flu) until it's too late. Those flu like symptoms indicate your body's immune system has lost the battle with the multiplying anthrax bacteria and you are about to die. The principal aim of militarized anthrax is to make spores that will not clump together (so they cannot be detected), will move easily in a breeze (so they can infect more people), and more virulent (so fewer spores are required to obtain a fatal infection) and be more resistant to antibiotics. An effective anthrax attack has to be one that is not detected, until the victims come down with the symptoms (at which time treatment with antibiotics is nearly useless.) Only Russia is known to have militarized grade anthrax. But even this stuff is not a super weapon, as an accidental release of it in 1979 did not kill all the local Russians it infected. In fact, nearly all the people killed were older or already ill from something else. In other words, healthy people with a robust immune system were able to deal with this militarized anthrax. But this accident happened in 1979, and since then the Russians have developed more potent strains of anthrax.
Natural anthrax is not a very good weapon. If you really want to hurt someone, use a gun or explosives. If the Unabomber had used anthrax instead of explosives, he would have done a lot less damage to his victims. But if terrorists get their hands on more powerful militarized anthrax, and these spores were released secretly in a subway or in densely populated area, the death toll would be in the thousands.