What Is It?

Produced by the bacterium clostridium botulinum, this agent is the most poisonous substance known to man. It can strike humans in two forms not relevant to bioterror: infantile botulism, which occurs when children less than 1-year-old ingest large amounts of the spore form; and wound-type botulism, which is very rare and occurs when an open wound comes into contact with the toxin. The high toxicity of botulinum toxin, its wide availability and the likely need for long-term medical care for victims make it an effective bioweapon, but it must be highly refined to work as an aerosol. About 60 percent of those left untreated from ingestional botulism die.

How Is It Spread?

The toxin can cause disease in humans through ingestion and inhalation, and can be spread via aerosol dissemination or the intentional contamination of foods or drinks. Contamination is the most likely method of attack, since trying to infect people via inhalation methods would be harder to carry out. The toxin is unstable in the environment and requires high levels of technical expertise to make it suitable for aerosol release. Botulism is not contagious; only those who ingest or inhale the main toxin will become ill.

What Are the Symptoms of Exposure?

Someone who ingests the toxin will have their nerve transmission affected and could have their muscles paralyzed. If someone eats something that contains the toxin, the first symptoms of paralysis appear within 12-36 hours after ingestion. Other symptoms include double vision, drooping eyelids, dry mouth and difficulty swallowing and talking. Paralysis spreads to the face and neck then works its way downward to the rest of the body, often leading to death from respiratory failure. Paralysis and disfiguring blisters are often the end result.

How Is It Treated?

A vaccine exists but is currently only used for lab workers and troops deployed to high-risk areas. It is in short supply and is very painful to receive. It's also not effective against all forms of the toxin.

A commercially available antitoxin, if given soon after a victim is diagnosed, can stop the spread of paralysis but won't reverse it. Other treatment, such as respiratory support, may be needed to keep someone alive. In general, paralysis will diminish eventually.

Physicians may try to remove contaminated food still in the gut by inducing vomiting or by using enemas. Wounds should be treated to remove the source of the toxin-producing bacteri, usually using surgical methods.

Who Has It/Where Can It Be Found?

Clostridium botulinum occurs naturally in soil. The Japanese cult Aum Shinrikyo couldn't produce an effective aerosol form of the toxin, although it had significant funding and scientific experts working on it. The Soviets also devoted resources to the weaponization of the toxin, and some supplies of it, as well as the scientists who produced them, are unaccounted for.

Iraq, North Korea, Iran, and Syria are believed to have developed botulinum toxin as a weapon. After the 1991 Gulf War, Iraq told U.N. weapons inspectors that it had produced 19,000 liters of concentrated botulinum toxin - enough, theoretically, to kill everyone on earth three times over.