2. Biological warfare programs open Pandora’s box. Bioweapons Starting in the 1950s, the United States and Russia began programs that turned the concept of controlling infectious diseases upside down. Instead of destroying disease vectors, military researchers developed technologies to make vectors and their toxins more effective. Cheaper and less destructive than hydrogen bombs, it was anticipated that “germ” weapons could achieve equally devastating effects . What Is a Bioweapon ? While humans are subject to a large number of infectious diseases, most of these diseases are not suitable for use as a bioweapon. To be effective, any bioweapon must meet three deceptively simple criteria: 1. The pathogen must be easy and safe to produce. One of the major perceived advantages of bioweapons over nuclear armaments was that they cost far less to manufacture. Because the pathogen will be required in large amounts—literally tons—it must be possible to scale up its production for reasonable cost, and to produce large amounts of it safely. 2. The pathogen must be hardy and practical to disperse. An infectious disease like typhus would make a poor bioweapon because it requires an insect vector—rat fleas—to spread it. An ideal pathogen would be composed of particles that are carried through the air like pollen, infecting those who breathe them. This suggests that the most effective bioweapons will be based on pathogens acquired through inhalation. 3. The pathogen must be effective. One use of a bioweapon is to incapacitate enemy troops on the battlefield. Soldiers that are violently ill rather than dead must be cared for, tying up the battlefield resources of your enemy. If this is the weapon’s intent, then it is important that the pathogen not kill those infected by it. Rather, they should stay quite ill so as to require intensive care. Quite the reverse is true, however, if the goal of the bioweapon is simply to kill large numbers of enemy troops. Such a pathogen should be as lethal as possible. Choosing a Bioweapons Agent Incapacitating Bioweapons. For an incapacitating bioweapon, military bioweapons developers have focused on four pathogens which rarely kill but produce devastating illness (table 1). One such bioweapon developed by the Russian military is based on tularemia, an animal disease that affects humans much like pneumonia. While severely debilitating, tularemia is rarely fatal. As a battlefield weapon, it has the disadvantage that symptoms do not appear until several days after exposure. To create an incapacitating bioweapon, the American military took a different approach. They developed a “cocktail” of three pathogens, chosen so that one acted very quickly, one a little later, and the third after a while and for a long time. The fast-acting agent was not a pathogen at all, but rather a toxin produced by one, staphylococcal enterotoxin B. Within a few hours of inhaling small amounts of this toxin, people suddenly become violently ill, running a very high fever for several days. Then the second agent kicks in, a virus disease called Venezuelan equine encephalitis which continues the fever, and adds nausea, vomiting, and diarrhea. After 10-12 days, the third agent takes over, a bacterial disease called Q fever which produces respiratory distress, acute headaches, and high fever persisting for three weeks or more. While totally incapacitating, this mixed-pathogen bioweapon is not lethal, killing fewer than one in a hundred. Lethal Non-Infectious Agents. For a lethal bioweapon that will kill anyone directly exposed to it, but no one else, there are really only two choices that satisfy all the requirements noted above. One is botulinum toxin, a highly poisonous protein manufactured by the bacteria responsible for food poisoning. This toxin is one of the most deadly chemicals known—a hundred millionth of a gram (a few molecules) is enough to kill you. As a bioweapon, it could be expected to kill large numbers of people, but would not be easy to administer on a battlefield without endangering one’s own troops. It is an ideal bioweapon for a terrorist intent on attacking a city, however, as it could be added to a community water supply and reach large numbers of people. Another lethal noninfectious bioweapon is pulmonary anthrax. Sometimes called “inhalational anthrax,” this deadly disease results from the inhalation into the lungs of spores from the bacterium Bacillus anthracis. Because it is so deadly (40-80% of infected individuals die) and spores offer a ready means of disseminating the disease, anthrax is the bioweapon of choice for killing large numbers of people on a battlefield without setting off an epidemic that might spread elsewhere. Lethal Infectious Agents. If the aim of a bioweapon is mass destruction—to kill very large numbers of people—then one of three infectious deadly pathogens are available. The least deadly, smallpox, is the weapon of choice. Smallpox would probably kill the greatest number of people, for while its mortality is only 30%, smallpox is highly infectious. Hemorrhagic fevers like Ebola have far higher mortality, sometimes exceeding 95%, but epidemics tend to spread only through half a dozen people before halting. Plague also has a high mortality, but is not easily spread from person to person. Only a small number of pathogens fit the requirements for a bioweapon, but those that do are terrifyingly apt. Table 1 Bioweapons These naturally-occurring pathogens are among those reported as having been developed into biological weapons by the United States or Russia. INCAPACITATING Q fever agent: Coxiella burnetii (a rickettsia-like bacterium) transmission: transmitted by ticks, by inhalation of the bacteria from animal hides, or by direct contact with infected farm animals. symptoms: an acute respiratory illness; onset is abrupt 10-12 days after infection; chills, throbbing headaches, and high fever (up to 104 degrees) may persist for 3 weeks or more. death: rarely fatal; peak mortality of untreated individuals is less than 1%. tularemia agent: Francisella tularensis transmission: a disease of rabbits, deer, and other animals transmitted by deerflies and ticks, or by direct contact. symptoms: ulcers and skin lesions, fever, and pneumonia appear 3-5 days after exposure. death: disease is disabling but rarely fatal; fewer than 5% of untreated cases die. horse encephalitis agent: Venezuelan equine encephalitis virus (VEE) transmission: transmitted from horses to humans, and among humans, by mosquitos. symptoms: severe headache, high fevers, nausea, vomiting, cough, and diarrhea, lasting for several days, followed by weeks of weakness and lethargy. death: in humans, not usually fatal; the peak mortality rate in untreated adults is less than 1%, in children 4%. LETHAL NON-INFECTIOUS pulmonary anthrax agent: Bacillus anthracis transmission: spores drifting in the air; a cattle disease transmitted to humans by spores; anthrax spores can be ingested, can infect the skin (cutaneous anthrax), or can be inhaled (pulmonary anthrax). symptoms: fever, fatigue, flu-like symptoms at first, followed within 6 days of exposure by severe breathing difficulty and turning blue. death: 24-36 hours after onset of severe symptoms. Peak untreated mortality: 40-80%. Treatable with antibiotics (penicillin, ciprofloxin, doxycycline) if given immediately after exposure. LETHAL INFECTIOUS pneumonic plague agent: Yersinia pestis (bubonic plague) Transmission: transmitted from one individual to another by rat fleas; in the absence of fleas, pulmonary form may be transmitted by exhaled air droplets to nearby individuals. symptoms: high fever, chills, and headache begin within 6 days of exposure and progress quickly to severe breathing difficulty and coughing up blood. death: within 2-4 days after onset of symptoms. Peak mortality if untreated approaches 95%. smallpox agent: Variola virus transmission: transmitted via exhalation of tiny droplets containing the virus that are then inhaled by others; highly contagious in the days immediately aftere the onset of the rash. symptoms: high fever, fatigue, headaches and backaches begin about 12 days after exposure, followed in 1-2 days by a rash and lesions on face, arms, and legs. death: within 2 weeks after onset of symptoms; peak mortality 40%. hemorrhagic fever agent: Marburg/Ebola viruses transmission: the natural reservoir of these Central African viruses are unknown; the virus is transmitted between individuals by contact with body fluids, and perhaps by respiratory transfer. symptoms: the virus infects the connective tissue lining blood vessels; the infection produces high fever, muscle aches, chills, and diarrhea within a few days, followed by shock and often by extensive bleeding. death: death occurs within a week of infection; peak mortality can be as high as 92%. TOXINS botulinum toxin agent: Clostridium botulinum symptoms: toxin attacks the cholinergic nervous system, causing death by paralysis. death: a deadly biochemical; contact with minute amounts (as little as a millionth of a gram) of toxin is fatal. staphylococcal enterotoxin B agent: Staphylococcus aureus symptoms: acts in 3-12 hours; produces chills, headache, and high fever (up to 106 degrees) for several days death: incapacitating but rarely fatal. next page