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Up to 30% of healthy people carry encapsulated pneumococci in their throat. Because of the effectiveness of the mucociliary escalator, these bacteria rarely reach the lung. The risk of pneu-

23.5 Bacterial Infections of the Lower Respiratory System

PERSPECTIVE 23.1 Terror by Mail: Inhalation Anthrax

During October and November 2001,22 human cases of anthrax were reported in the United States, half due to inhalation of Bacillus anthracis spores (inhalation anthrax) and half due to skin infections (cutaneous anthrax). Five deaths occurred, all among the inhalation cases, and more than 30,000 individuals potentially exposed to the spores were given antibiotic treatment as a preventive. Most of the anthrax cases could reasonably be linked to four envelopes containing purified spores of B. anthracis, which contaminated people, air, and surfaces during their journey through the postal system to their destinations. Only 18 cases of inhalation anthrax were identified in the United States during the entire twentieth century, the most recent in 1976.

Sometimes called "anthrax pneumonia," inhalation anthrax victims generally fail to show the hallmarks of pneumonia. Inhaled B. anthracis spores are quickly taken up by lung phagocytes and carried to the regional lymph nodes, where they germinate, kill the phagocytes, and invade the bloodstream. Although the organisms are susceptible to various antibacterial medications, treatment must be given as soon as possible after infection, because the bacteria produce powerful toxins that usually kill the victim within a day or two after bloodstream invasion occurs. Cutaneous anthrax and anthrax acquired by ingesting contaminated meat are much less likely to be fatal.

Bacillus anthracis endospores have long been considered for use in biological warfare.The organism is readily available; anthrax is endemic in livestock in most areas of the world including the United States and Canada. The spores are easy to produce and remain viable for years. When anthrax is acquired by inhalation, the fatality rate approaches 90%, yet the disease is easily confined to the attack area because it does not spread person-to-person. Bacillus anthracis spores were employed as a weapon as early as World War I, although ineffectively, in an attack on livestock used for food. Just prior to World War II, Japan, the United States, USSR, Germany, and Great Britain secretly began to develop and perfect anthrax weapons, but they were not used during the war. During the "cold war"that followed, both the United States and the USSR developed massive biological warfare programs that employed many thousands of people, perfecting techniques for preparing the spores and delivering them to enemy targets. An executive order by President Nixon ended the U.S. program in 1969, and the stockpiled weapons were ordered destroyed, but other countries continued weapon development. In 1979, an accidental discharge of B. anthracis spores, a weight equaling about two paper clips, from a biological warfare plant at Sverdlovsk, USSR, caused more than 90 deaths downwind of the facility. The 1990 war with Iraq exposed their sizeable anthrax weapon program, and several times during the 1990s a Japanese terrorist group tried ineffectively to attack Tokyo institutions with anthrax spores.

During this long history of anthrax weapon development, remarkably little was accomplished that would help defend against an attack, presumably because the best defense was considered an opponent's fear of counterattack. As a result of the 2001 anthrax-by-mail incident a number of questions came into focus and the answers vigorously sought. How do you diagnose anthrax quickly, by history, physical examination, and x-ray, and what is the best way to teach and organize medical practitioners to meet an anthrax attack? What tests are available to identify B. anthracis rapidly and reliably, and what is the best way to sample people and the environment? How can decontamination of buildings and other objects be accomplished? Is there sufficient vaccine available, can better vaccines be developed, and what is their role before or after exposure to B. anthracis? What is the best antimicrobial treatment, is there enough of it, is it readily accessible, and how long should it be given to exposed individuals? Are other potential treatments such as antitoxins and designer medications to block the lethal effect of B. anthracis toxins being developed?

Some of these questions were answered within months of the attack, and with more answers on the horizon we should be prepared for what possibly could be more extensive anthrax assaults.

mococcal pneumonia rises dramatically when this defense mechanism is impaired, however, as it is with alcohol and narcotic use, and with respiratory viral infections such as influenza. There is also an increased risk of the disease with underlying heart or lung disease, diabetes, and cancer, and with age over 50.

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