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For many years, emergency service terrorism training programs have warned about the potential use of biological materials by terrorists. Anthrax threats had become the bomb threats of the late 1990s and the new century. All of those threats had been hoaxes.
But on Oct. 2, 2001, in Palm Beach County, FL, the potential use of biological agents, in particular, anthrax became a reality. The appearance of a case of rare inhalation anthrax set off alarm bells in the minds of many in the emergency response community. Inhalation anthrax is so rare that only 18 cases occurred in the United States during the 20th century.
Anthrax is not a contagious disease and is not transmitted from person to person. It can be acquired through three routes of entry into the body: inhalation, ingestion and cutaneous. Inhalation anthrax occurs when spores are aerosolized and breathed into the lungs. Ingestion anthrax results from eating contaminated meat. Cutaneous anthrax results from spores entering the body through breaks in the skin. Approximately 95% of all accidental anthrax cases in the world are the cutaneous form.
Cutaneous anthrax occurs naturally among farmers, ranchers and veterinarians as a result of contact with infected livestock. In August 2000, some 30 head of cattle in Nevada died from anthrax. It is believed that the anthrax was contracted when ditch-clearing operations released soil-borne spores onto pasture grasses. In September 2000, a family in Minnesota was reported to have contracted ingestion anthrax from eating infected beef, which they had butchered and processed themselves.
Anthrax was one of the first diseases identified in the field of microbiology in 1876, and the first disease for which an effective live bacterial vaccine was developed, in 1881 by Louis Pasteur. Inhalation anthrax was discovered in the late 19th century. Natural outbreaks of inhalation anthrax occurred among wool sorters in England, becoming one of the first occupational respiratory infectious diseases. Processing of contaminated goat hair and alpaca wool resulted in the generation of infectious aerosols.
The largest human exposure of inhalation anthrax occurred in Sverdlovsk, Russia, in 1979. Anthrax spores were released accidentally from a military research facility upwind from the outbreak. Cases were also reported in animals located more than 30 miles from the site. There were 66 documented human deaths and 11 injuries as a result of the release, though it is believed by many that the death count may have been much higher.
Anthrax The Disease
Bacillus anthracis is a Gram-positive, spore-forming bacillus that can survive for over 100 years in the spore form. Bacteria are classified as Gram-positive or Gram-negative based on their response to the Gram staining procedure. The primary difference between Gram-negative and Gram-positive bacteria occurs in the cell wall. Gram-positive cell walls are usually much thicker and more difficult to penetrate than Gram-negative cell walls. Bacillus is a genus of bacteria that is found everywhere in nature (in soil, water and airborne dust). Spores are not formed in living tissue. When a host dies and the disease is exposed to oxygen during the decay of the corpse, the spores are formed. Development of spores is a survival system, which allows the bacteria to survive in nature until a suitable host is once again contacted.
During World War II, the British conducted tests with anthrax on Gruinard Island off the coast of Scotland. The island remained contaminated with anthrax spores and uninhabitable until 1986, when tons of topsoil were removed. The island decontaminated by soaking the remaining soil with seawater spiked with large amounts of formaldehyde.
It is not known exactly how many spores are necessary to cause cutaneous anthrax in humans. The only data available is from animal tests. Ken Alibek, a defector from the former Soviet Union’s biological weapons program, believes 10 to 15 spores could cause disease.