Anthrax is a bacterial disease caused by Bacillus anthracis. In the absence of proper nutrients but in the presence of oxygen, the bacteria form hardy, environmentally stable spores that cause infection in cattle and other hoofed mammals.

These same spores of B. anthracis can cause three forms of the disease in humans--dermal, inhalation, or gastrointestinal anthrax--depending on whether the spores are taken into the body through cuts in the skin, are breathed in, or are consumed in tainted meat from diseased animals.

There are many strains of B. anthracis and not all are virulent. Anthrax is not contagious. Dermal anthrax is the most common form in humans and is treatable with a variety of antibiotics. Gastrointestinal anthrax is not very common and responds well to early antibiotic treatment, but the mortality rate is very high if left untreated.

Inhalation anthrax, which requires from 8,000 to 10,000 spores to cause infection, is very rare in the U.S. A single case--like the Florida man who died from it--raises a red flag. By the time the first flulike symptoms are evident, antibiotic treatment is too late. Untreated, the mortality rate is nearly 90%.

A controversial vaccine for anthrax exists, but it is reserved for military personnel, meatpackers, and researchers working with anthrax and was approved only for the dermal form of the disease. It probably wouldn't be effective against anthrax bioengineered as a weapon of war.

Sophisticated technical expertise is required to make anthrax into a weapon. Only a relatively few nations have been able to do so. A Japanese cult tried and failed. Terrorist groups may be trying to get such weapons, but no publicly available information confirms that they have.

The recent outbreak of anthrax in the U.S. could just as likely be the work of an individual or a few individuals. Anthrax can be obtained from the soil and disseminated crudely to produce some casualties. An aerosol cloud of finely milled spores delivered via a ventilation system or a weapon is needed to produce mass casualties.

At press time, only 45 people in Florida, New Jersey, New York, and Washington have likely been exposed to anthrax. Exposure does not mean they have the disease, and many of those testing positive in Washington may not even have been exposed to anthrax. Preliminary results using standard microbiological tests on cultured suspected material produce a high number of false positives.

Of the 45, only two people in Florida have contracted inhalation anthrax; one has died and the other, given antibiotics before symptoms appeared, is hospitalized and expected to live. Three people in New York and a New Jersey postal worker have the dermal form of the disease, are taking antibiotics, and are expected to recover fully.

Preliminary tests show the New York and Florida strains to be nearly identical, though government officials will not identify the strain. Officials say the Washington anthrax is a common strain, not particularly virulent, and responds to antibiotics.

The source for the New York and Washington outbreaks has been determined to be powder in envelopes. Officials suspect mail as the likely source of the Florida outbreak, but they are not absolutely certain. Ambiguous test results of the tainted Nevada letter leave officials unable to say even if anthrax was present or not.

It isn't known whether the same strain of anthrax caused all the outbreaks, what that strain is, or where it originated. The identity of the precise tests performed at the various state health labs or by CDC, the Army's infectious disease research lab, or the FBI is another unknown. Among the other unknowns are: whether the same sample was tested separately by two different labs to eliminate errors and contamination, the chain of custody of the samples, and how they were handled and shipped.

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Copyright © 2001 American Chemical Society