During the recent past there has been concern about the possibility of terrorist attacks using biological weapons. This concern has been heightened by the occurrence of a case of "inhalation anthrax" in Florida, in association with the identification of the same anthrax spores in the nose of two fellow employees and its detection on the victim's computer keyboard. Prior to the Florida incident, there have been hundreds of mailed or telephoned bioterrorism threats, usually claiming that anthrax had been released. All were hoaxes resulting in thousands of potential victims being treated with antibiotics and decontamination procedures. These hoaxes prove to be extremely costly both in terms of concern and dollars.

There are numerous biological agents that could potentially be used as terrorist weapons including Bacillus anthracis (anthrax), smallpox, Francisella tularensis (tularemia), Yersinia pestis (plague) and botulinum toxin from Clostridium botulinum. Of these, anthrax is felt to be the most likely organism to be used for such purposes. The likelihood that these agents could be used as a bioterrorist weapon is possible but unlikely. In fact, even though anthrax has been at the top of the list of "the most likely agent to be used in a bioterrorist attack", to the best of our knowledge, other than the one possible case as a result of an intentional release of anthrax in Florida , this agent has never been successfully used in bioterrorist attacks.

Anthrax is a serious bacterial infection that occurs when Bacillus anthracis spores enter the body through abrasions in the skin or by inhalation or ingestion. Most mammals, especially plant eating animals that graze for food (eg. cattle, goats, sheep, camels), can develop infecton. Human infections result from contact with contaminated animals or animal products, and there are no known cases of human-to-human transmission. Human anthrax is not common. Only 18 cases of inhalation anthrax have been reported in North America in the last century, the last case being in 1976. Cases of cutaneous anthrax have occurred previously in North America, usually related to spores on goat or sheep hair imported from counties where anthrax is endemic. Cutaneous anthrax, the most common form, is usually curable when treated with antibiotics. Systemic infection resulting from inhalation of the organism (inhalation or pulmonary anthrax) has a very high mortality rate, with death usually occurring within a few days after the onset of symptoms. When initiated early during the incubation period, antibiotics are very effective in treating anthrax. The rapid course of the disease once symptoms appear make early treatment an absolute necessity.

Humans can acquire anthrax by agricultural or industrial exposure to infected animals or animal products either by direct contact or by breathing in spores released from hides or hair. More recently, the potential for intentional release of anthrax spores in the environment has caused much concern. However, creating a form of anthrax that would be able to be aerosolized is difficult since the spores have a natural tendency to clump together and not remain in the air. In addition, the environmental conditions (i.e., air movement and humidity) must be exact in order to ensure adequate aerosolization. The fact that an apparent bioterrorist attack in Florida only resulted in illness in one person is evidence for the difficulty in weaponizing this agent. One terrorist group in Japan, dispersed aerosols of anthrax and botulism in Tokyo on at least 8 occasions without producing any illness in the citizens of Tokyo.

Whether introduced in a letter or released in the environment directly, the success of distributing a large enough amount of anthrax spores to infect large numbers of individuals in a single building or closed environment would be very unlikely. Air sampled in goat-hair-processing plants was found to be contaminated with spores, yet workers did not come down with disease. It is thought that in order to infect 50% of persons that an exposure of between 8,000 and 10,000 spores would be required.

Typically, if anthrax was used in a bioterrorist attack, terrorists would be attempting to cause inhalation anthrax-that is the type that causes disease after exposure to aerosolized anthrax. Inhalation anthrax usually presents in two phases. The incubation period is from 1 to 6 days. The initial stage, continuing for an average of 4 days, begins with the insidious onset of muscle aches, malaise, fatigue, nonproductive cough, and fever. There may be a transient improvement after the first few days. The second stage, lasting 24 h and often culminating in death, develops suddenly with the onset of acute respiratory distress. Meningitis occurs in up to 50% of cases.

There has been much concern about how individuals can protect themselves if anthrax is introduced into an environment or someone becomes infected. Stockpiling gas masks and antibiotics is not the answer. Do not touch suspicious packages, report them immediately to the appropriate authorities, and co-operate with individuals whose responsibility it is to implement emergency procedures if exposure has occurred.

Transmission of anthrax from an infected person to another individual has never been described. Infected people do not excrete enough spores to cause a danger to people who care for them. Their blood and body fluids are not infectious. Therefore there is no concern about coming in contact with persons infected with anthrax once post-exposure decontamination procedures have been performed. In health care settings no additional precautions are necessary in providing care to these individuals and there is no risk to friends or families of patients with the disease.

Hospitals, laboratories, public health departments and emergency service personnel have a role to play in early identification and detection of possible bioterrorism threats. Emergency room staff and first responders need to be alert for the appearance of unusual presentations of common disease (i.e., pneumonia) or clusters of cases of common diseases. Laboratories should be prepared to process clinical specimens and identify potential pathogens, such as B. anthracis. Public Health organizations are ready to manage exposed individuals and environments in the event of a suspected bioterrorism attack.

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