Cause
Bacillus anthracis is a bacterium that lives in soil and has developed a survival tactic that allows it to endure for decades under the harshest conditions. An anthrax bacterial cell can transform itself into a spore, a very hardy resting phase which can withstand extreme heat, cold, and drought, without nutrients or air. When environmental conditions are favorable, the spores will germinate into thriving colonies of bacteria. For example, a grazing animal may ingest spores that begin to grow, spread, and eventually kill the animal. The bacteria will form spores in the carcass and then return to the soil to infect other animals in the future.
While its spore form allows the bacteria to survive in any environment, the ability to produce toxins is what makes the bacteria such a potent killer. Together, the hardiness and toxicity of B. anthracis make it a formidable bioterror agent. Its toxin is made of three proteins: protective antigen, edema factor, and lethal factor.
- Protective antigen binds to select cells of an infected person or animal and forms a channel that permits edema factor and lethal factor to enter those cells.
- Edema factor, once inside the cell, causes fluid to accumulate at the site of infection. Edema factor can contribute to a fatal build-up of fluid in the cavity surrounding the lungs. It also can inhibit some of the body’s immune functions.
- Lethal factor also works inside the cell, disrupting a key molecular switch that regulates the cell’s functions. Lethal factor can kill infected cells or prevent them from working properly.
Bioterror Connection
In the fall of 2001, lethal anthrax bacteria were spread deliberately through the U.S. mail. Twenty-two people became ill, and five died. The perpetrator has not been caught.
Even before this bioterror attack, public health officials were concerned about the potential for such an event. In 1999, the Centers for Disease Control and Prevention (CDC) created lists of high-priority biological agents that terrorists could use to harm civilians. An expert panel of doctors and scientists classified Bacillus anthracis as a Category A bioterror agent. The NIAID list of Category A organisms includes those that pose the greatest threats to national security due to their ease of transmission, high rate of death or serious illness, potential for causing public panic, and the special public health measures an epidemic would require.
Since the creation of the CDC lists, public health officials and researchers have worked to plan and prepare for a possible bioterror attack. Following the 2001 anthrax attacks, federal funding for these efforts increased significantly.
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