Bioterrorism refers to the use of lethal biological agents to wage terror against a civilian population. It differs from biological warfare in that it also thrives on public fear, which can demoralize a population. An example of bioterrorism is the anthrax outbreak that occurred during September-November 2001 in the United States. Anthrax spores intentionally spread in the mail distribution system caused five deaths and a total of 22 infections.


The Centers for Disease Control (CDC) classifies bioterror agents into three categories:

A laboratory technician holding an anthrax laced letter, after safely opening it, addressed to Senator Leahy at Fort Detrick bio-medical research laboratory in the Amerithrax investigation.

A laboratory technician holding an anthrax laced letter, after safely opening it, addressed to Senator Leahy at Fort Detrick bio-medical research laboratory in the Amerithrax investigation. The 2001 Anthrax Attacks occurred over the course of several weeks beginning on September 18, 2001, one week after the September 11 attacks. Letters containing anthrax spores were mailed to several news media offices and two Democratic Senators (Tom Daschle and Patrick Leahy), killing 5 people and infecting 17 others.
(FBI/Science Source)

Using disease as a weapon is not a new idea. It goes back at least hundreds of years and possibly much further. One account of the beginning of the great plague epidemic in fourteenth-century Europe that killed one-third of the population states that it started with an act of bioterrorism, as reported by A. Daniels in National Review. The Tartars were attacking a Genoan trading post on the Crimean coast in 1346 when the plague broke out among them. Turning the situation into a weapon, the Tartars catapulted the dead and diseased bodies over the trading post walls. The Genoans soon developed the deadly disease and took it back with them to Genoa, where it soon engulfed all of Europe. Another example from early North American history is provided by the British soldiers who deliberately gave smallpox-infected blankets to Native Americans in the 1700s.

The Hague Conventions of 1899 and 1907 included clauses outlawing the deliberate spread of a deadly disease. Despite these international treaties, during World War I, German soldiers attempted to infect sheep destined for Russia with anthrax. After the war, forty members of the League of Nations, the precursor of the United Nations, outlawed biological weapons. But many countries continued biological warfare research. During World War II, the Japanese mass-produced a number of deadly biological agents, including anthrax, typhoid, and plague. They infected water supplies in China with typhoid, killing thousands, including 1,700 Japanese soldiers. Bioterrorism entered popular literature more than a century ago when British science fiction writer H. G. Wells (1866–1946) wrote The Stolen Bacillus, a novel in which a terrorist tries to infect the London water supply with cholera, an acute and often deadly disease.

Throughout the Cold War era, several nations, including the United States and Soviet Union, developed sophisticated facilities to produce large amounts of biological agents to be used as weapons. Most nations have renounced the manufacture, possession, or use of biological weapons. However, a few rogue nations, including Iran, Iraq, and North Korea, still have active biological warfare programs according to the U.S. military. Many experts in the field believe that terrorists can obtain deadly biological agents from these rogue nations or from other terrorist or criminal groups active in nations of the former Soviet Union.

What many consider an act of bioterrorism by domestic terrorists occurred in Dalles, Oregon, in 1984. Members of a religious cult contaminated restaurant salad bars with Salmonella typhimurium, a nonlethal bacterium that nonetheless infected 751 people. The incident was reportedly a trial run for a more extensive attack to disrupt local elections later that year. The 2001 anthrax attacks in the United States were very limited in scope compared to the potential damage that could result from large-scale bioterrorism.


A large-scale bioterrorism attack on the United States could threaten vital national security interests. Massive civilian casualties, a breakdown in essential services, violation of democratic processes, civil disorder, and a loss of confidence in government could compromise national security, according to a report prepared by four nonprofit analytical groups, including the Center for Strategic and International Studies and the Johns Hopkins Center for Civilian Biodefense Studies.

An added concern is that most physicians have never treated a case of a bioterrorism agent such as smallpox or Ebola. This is likely to cause a delay in diagnosis, further promoting the spread of the contagious agent. For example, based on past smallpox history, it is estimated that each person infected during the initial attack will infect another ten to twelve persons. In the case of smallpox, only a few virus particles are needed to cause infection. One ounce of the smallpox virus could infect 3,000 persons if distributed through an aerosol attack, according to William Patrick, the senior scientist for the United States biological weapons program (program terminated in 1969) in a 2001 Washington Post Magazine interview. Given these numbers, a terrorist with enough smallpox virus to fill a soda can could potentially infect 36,000 people in the initial attack who could then infect another 360,000–432,000. Of these, an estimated 30 percent or 118,800–140,400 would likely die. The disease itself may only play a small role in this death toll, as the shear number of cases would overwhelm medical infrastructure, and triaging systems would be used to label people who would be treatable under other circumstances as too far gone to treat.

Type of biological agents

Among the Category A Diseases/Agents, six highly lethal biological agents are most likely to be used by terrorists, according to the CDC. Depending on the biological agent, disease could be spread through the air, or by contaminating the food or water supply. Scientists are conducting research to develop methods of detection for bioterrorist attacks. Methods of real-time outbreak detection of diseases are referred to as biosurveillance. Researchers at the University of Pittsburgh Center for Biomedical Informatics developed an automated detection system in 1999. The system, Real-Time Outbreak Disease Surveillance (RODS), is able to access and collect data from hospitals, clinic, laboratories, and pharmacies for early detection of a potential bioterrorism attack. U.S. President George W. Bush issued a proposal to provide biosurveillance detection systems for all fifty states as part of the Public Health Security and Bioterrorism Preparedness and Response act of 2002. Other software programs have been developed for advanced detection such as Electronic Surveillance System Early Notification for Community-Based Epidemics (ESSENCE), Early Aberration Response System (EARS), Biowatch, and Bioshield. Biosense is a surveillance system used by the U.S. Center for Disease control. As of 2008, about more than one hundred sites in the United States were employing at least one method of biosurveillance.


The possibility that bioterrorists may strike at food and water supplies is of serious concern to health and environmental officials. Such an attack could be initially perceived as unintentional food poisoning, which might delay recognition of the outbreak, and complicate identification of the contaminated food.

According to an article in The Lancet in May 2002, the United States food supply had become so centralized that an act of deliberate tampering of a widely dispersed food product could cause a widespread outbreak. The article also stated that the anthrax letter attacks of 2001 have shown that even a small biological attack can produce considerable public nervousness and challenge the healthcare system.

The U.S. Department of Homeland Security has developed strategic plans to respond to acts of bioterrorism. These include prevention efforts such as routine checks of reservoir water and domestic and imported foods. These safeguards increase the likelihood that any threat to potable water and food supplies would be found before people exhibit symptoms, and also that a disease can be traced back to its source, decreasing the spread and severity of illness. Hospitals and major treatment centers have their own emergency protocols to address emergency situations like bioterrorist attacks. Stockpiles of vaccines and routine training for first responders are other ways systems can protect themselves from bioterrorism.

See also Anthrax ; Chemical poisoning ; Cholera ; Ebola virus disease ; Plague ; Smallpox .



Ryan, Jeffrey, and Jan Glarum. Biosecurity and Bioterrorism: Containing and Preventing Biological Threats (Butterworth-Heinemann Homeland Security). Burlington, MA: Butterworth-Heinemann, 2008.


Centers for Disease Control and Prevention. “Bioterrorism Agents/Diseases.” (accessed June 12, 2018).

World Health Organization. “Bioterrorism.” (accessed October 1, 2012).


Center for the Study of Bioterrorism and Emergency Infections-Saint Louis University, 3545 Lafayette, Ste. 300, St. Louis, MO, 63104, .

Centers for Disease Control and Prevention—Bioterrorism Preparedness & Response Program (CDC), 1600 Clifton Rd., Atlanta, GA, 30333, (404) 639-3534, (888) 246-2675,, .

Texas Department of Health Bioterrorism Preparedness Program (TDH), 1100 W 49th Street, Austin, TX, 78756, (512) 458-7676, (800) 705-8868, .

Ken R. Wells
Alyson C. Heimer, MA

  This information is not a tool for self-diagnosis or a substitute for professional care.