The Mongols and the British troops did not know that certain microorganisms cause disease. They knew only that disease was rumored to have spread from dead bodies or, in the case of smallpox, even from the blankets that touched victims. People did not know that microorganisms cause infectious disease until 1876, when the German scientist Robert Koch (1843–1910) proved that anthrax (AN-thraks) bacterium causes the disease anthrax *
Many people believe that well-funded terrorists can afford to purchase equipment to build biological weapons or that it will be sold when ordered. Some countries—especially those harboring or supporting known terrorist groups—continue to manufacture and store stockpiles of dangerous microorganisms. The use of bioterrorism to wage warfare is favored among terrorists because it requires few resources compared with traditional warfare and can potentially harm large numbers of people.
How Can Biological Agents Be Spread?
Deadly microorganisms (also known as biological agents or bioweapons) can be spread purposely through the air or food and water supplies, or by intentionally infecting someone with a highly contagious agent and letting that person circulate in a community, starting a massive wave of disease. The agent could be disseminated in any busy public place with the intention of infecting many people who then travel to various destinations unintentionally spreading the disease.
Some organisms can be aerosolized (AIR-o-suh-lized), meaning that they are processed into the tiniest of particles, in a wet or dry form, that can be sprayed or released into the air so that large numbers of people can inhale them. Aerosolized organisms can be dispersed by aerosol containers, small crop-dusting planes, ventilation systems, or contamination of an object that can carry disease throughout a region, such as the anthraxtainted letters received by various government and media employees in the United States.
The handling and release of many of these organisms are dangerous and could be deadly for potential terrorists trying to use them. Some harmful biological organisms become weakened as they spread into water or food supplies, making them less likely to cause significant harm to anyone who comes into contact with them. For example, a person would have to inhale thousands of anthrax spores * to become sick. A terrorist group trying to use anthrax as a bioweapon would have to use a highly concentrated form to be able to harm large numbers of people via contaminated packages or envelopes. Some bioterrorism agents, such as the smallpox virus, can be spread from person to person.
What Are Potential Biological Agents?
The Centers for Disease Control and Prevention (CDC) separates biological organisms into categories according to their virulence (VEER-uh-lents), or ability to cause disease. Potential biologic agents used for terrorism are divided into three categories.
Category A, or high-priority agents, can be easily disseminated or transmitted from person to person, cause high death rates, cause public panic and social disruption, and require special action for public health preparedness. Category A agents include:
- Anthrax. Anthrax is caused by the bacterium Bacillus anthracis. The bacteria form spores, which are found in soil and have a hard coating that allows them to survive in harsh environments. The disease is not contagious from person to person, and natural human infection is rare. There are three types of anthrax: cutaneous (kyoo-TAY-nee-us) anthrax, which infects the skin; inhalation (in- huh-LAY-shun) anthrax, which results from breathing in large numbers of concentrated spores; and gastrointestinal * anthrax, which is caused by ingesting (eating) spores. An anthrax vaccine exists but requires many injections and has side effects. Antibiotics may be given for prevention.
- Smallpox. Smallpox, a deadly viral infection, is caused by the variola virus and is found only in humans. Smallpox is the most contagious disease known and is transmitted through direct contact with the lesions * of an infected person, by inhaling infected droplets of moisture released into the air by coughing patients, and even by handling contaminated clothing that contains fluid from smallpox sores. The symptoms of smallpox are high fever, headache, backache, vomiting, and a painful rash of lesions that covers the face, arms, and body and often leaves scars. The disease is fatal in up to 30 percent of cases. In the early 20th century smallpox claimed millions of lives, but in 1980 the World Health Organization (WHO) declared the disease was eradicated from the human population following an aggressive worldwide vaccination * program. Routine vaccination against smallpox in the United States ended in 1972. The CDC keeps an emergency supply of smallpox vaccine * in the event that bioterrorism attacks with smallpox occur in the United States. In 2002 some vaccine-making companies received approval from the CDC to make an additional supply of the vaccine should it be needed on a more widespread basis.
- Botulism toxin. Botulism is caused by the toxin * produced by the bacterium Clostridium botulinum. The bacteria can be inhaled or swallowed, or they can enter the body through a wound, but the disease is not contagious from person to person. The toxin produced by the bacteria affects the nervous system, causing nerve damage and temporary paralysis * , including the muscles for speaking, swallowing, and breathing. Botulism can lead to respiratory failure * and even death. The bacterium and its toxin could be used to produce bioweapons. An antitoxin * * ; septicemic plague enters the bloodstream, causing internal bleeding and shock * ; and pneumonic plague infects the respiratory tract * . The last form is potentially important in biological warfare because Yersinia pestis bacteria can remain alive in the air for up to an hour, making aerosolized transmission possible. Yersinia pestis is found in rats and other rodents in all parts of the world, including the United States. Plague can spread from infected rats to humans by direct bites or from fleas. The pneumonic form of plague is the only kind that is contagious among humans; transmission takes place when someone has close contact with an infected person who is coughing or sneezing. Symptoms of the plague include fever, chills, headache, abdominal pain, painful and swollen lymph nodes (called buboes, BYOO-boze), chest pain, coughing, bloody sputum * , and septic shock * . There is no vaccine available in the United States, but antibiotics can treat the disease successfully if diagnosed early.
- Tularemia. Tularemia, also known as rabbit fever, is caused by the bacterium Francisella tularensis and is highly infectious. The disease is not contagious among humans, and human infection is rare. Tularemia can be transmitted through contact with infected animals or contaminated water or soil. The disease is potentially dangerous as a biological weapon because even small numbers (fewer than 10 to 50) of the aerosolized bacteria can cause serious disease, such as life-threatening pneumonia
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Category B
Category B agents are moderately easy to disseminate, can cause moderate morbidity (rates of disease) and low mortality (rates of death), and require specific action from the CDC. The following are category B agents:
- Brucellosis. Bacteria of the genus Brucella cause disease in various vertebrates such as sheep, goats, cattle, deer, elk, pigs, and dogs. Contact can infect humans and cause a range of symptoms similar to the flu, although central nervous system (CNS) and heart infections are common. Brucellosis is only one example of a zoonotic disease, one that can be passed from animals to humans.
- Tetanus toxin. The epsilon toxin of Clostridium perfringens, the organism that causes tetanus * , is a Class B toxin.
- Food safety threats. Bacteria such as salmonella, shigella, and E. coli could be used deliberately to contaminate foods as a bioterrorist act.
- Q fever. Q fever is a rickettsial * zoonotic disease caused by Coxiella burnetii. Animals affected are sheep, goats, and cattle, but humans can inhale particles contaminated with the organism, which is resistant to heat and highly infectious by the aerosol route. A single inhaled organism can cause illness.
- Venezuelan equine encephalitis (VEE). Horses contract VEE through bites from infected mosquitoes. It is highly infectious but not particularly stable when spread by aerosol, and it does not persist for a long time.
- Psittacosis. Psittacosis (sit-a-CO-sis), also called parrot fever, is a bacterial disease caused by Chlamydia psittaci, and it is transmitted from birds to people when people inhale dried bird feces. This disease could be easily aerosolized as a biological warfare agent.
- Water supply threats. Cholera is a well-known diarrheal disease caused by Vibrio cholera, acquired through drinking contaminated water. It could be spread by aerosols, but more likely it would be through contaminated food or water supplies.
- Ricin toxin. Ricin (RY-sin) toxin is made from castor beans. It has high terrorist potential because it is available, easy to process, and is well known as a bioterrorism agent.
Category C are third-priority agents that may be easily available and could be genetically engineered to have high potential for a public health impact. Examples are as follows:
- Nipah virus. Nipah (NIE-pa) virus infects pigs and humans. In people it can cause a sometimes fatal form of viral encephalitis
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How Can People Protect Themselves?
Throughout the late 20th century, most biological defense strategies were meant to protect soldiers on the battlefield rather than ordinary people in cities. In 1999 the University of Pittsburgh deployed the first automated bioterrorism detection system, called Real-Time Outbreak Disease Surveillance (RODS). RODS was designed to collect data from places such as hospital clinics, laboratories, 911 calling centers, veterinary clinics, ranching and feedlot operations, food processors, drinking-water systems, school attendance records, and over-the-counter drug sales and use them to detect a terrorist event at the earliest possible moment.
The U.S. Department of Homeland Security was formed in late 2002 to oversee the government's preparation for and defense against potential acts or threats of bioterrorism that might occur in the United States. There was an increase in federal stockpiles of antibiotics to treat anthrax, plague, tularemia, and other potential bioweapons, as well as the production of additional supplies of smallpox vaccine. Research continued in the development of better medical treatment and the creation of vaccines to protect people against biological agents. Medical professionals and emergency response teams were trained to diagnose diseases and to respond quickly to epidemics that could result from bioterrorism. The following situations were believed to indicate the possibility of an outbreak:
- Notice of a disease or strain that is not normally within the population
- Patterns of resistance to antibiotics
- Symptoms among patients that are not typical of any disease or disorder
- Diseases occurring in ways inconsistent with their typical geographical location. For example, a tropical disease might occur in a northern city
- Other strange findings, such as a large number of cases, high illness or death rates, and changes from normal disease occurrences
Researchers have experimented with high-tech devices, such as tiny electronic boxes that contain living nerve cells, to detect the presence of bacterial toxins. They also have used fiber-optic tubes lined with antibodies coupled to light-emitting molecules that can identify specific pathogens, such as anthrax. The technology of genetic engineering * could produce a bacterial agent to target a particular genetic group or geographical population.
Radiation as a Bioterrorism Agent
The harmful effects of radiation are well documented and are viewed as being an agent of bioterrorism since the development of the “dirty bomb.” A dirty bomb is a type of explosive that is mixed with radioactive substances. When the bomb is detonated, it carries radioactive material into the environment. This radioactive material can cause illness and diseases.
Radiation is a carcinogen (kar-SIN-o-jen), which means it is a cancer-causing agent. Exposure to very high doses of radiation increases the risk of injury or illness. Problems may include:
- Radiation burns on the exposed parts of the body
- Genetic diseases or intellectual disability in children whose mothers were exposed during pregnancy
- Cancer of the bone marrow, thyroid, lung, breast, and kidney from long-term exposure to low levels of radiation
- Lung cancer that may result from radon accumulating in basements and sticking to dust that people inhale
- Damage to blood vessels and the brain, infection, and bleeding from whole-body exposure to very high doses of radiation, which usually leads to death
The severity of the symptoms from radiation exposure depends on the source of the radiation, the dose, the rate of absorption into the body, and the sensitivity of the body tissue affected. A large dose of radiation can lead to cell death over hours, days, or weeks.
See also Bacterial Infections • Botulism • Ebola Virus Disease • Hantavirus Pulmonary Syndrome • Plague • Radiation Exposure • Rickettsial Infections • Tetanus (Lockjaw) • Tuberculosis • Tularemia • Zoonoses: Overview