“Biological weapons.” The phrase alone could send chills down the spine. But what are they? How do they work? And are we really at risk? In this Spotlight, we survey their history and potential future.

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Biological warfare has been used for thousands of years.

Sometimes known as “germ warfare,” biological weapons involve the use of toxins or infectious agents that are biological in origin. This can include bacteria, viruses, or fungi.

These agents are used to incapacitate or kill humans, animals, or plants as part of a war effort.

In effect, biological warfare is using non-human life to disrupt — or end — human life. Because living organisms can be unpredictable and incredibly resilient, biological weapons are difficult to control, potentially devastating on a global scale, and prohibited globally under numerous treaties.

Of course, treaties and international laws are one thing — and humanity’s ability to find innovative ways of killing each other is another.

The history of biological warfare is a long one, which makes sense; its deployment can be a lo-fi affair, so there is no need for electrical components, nuclear fusion, or rocket grade titanium, for instance.

An early example takes us back more than 2 and a half millennia: Assyrians infected their enemy’s wells with a rye ergot fungus, which contains chemicals related to LSD. Consuming the tainted water produced a confused mental state, hallucinations, and, in some cases, death.

In the 1300s, Tartar (Mongol) warriors besieged the Crimean city of Kaffa. During the siege, many Tartars died at the hands of plague, and their lifeless, infected bodies were hurled over the city walls.

Some researchers believe that this tactic may have been responsible for the spread of Black Death plague into Europe. If so, this early use of biological warfare caused the eventual deaths of around 25 million Europeans.

This is a prime example of biological warfare’s potential scope, unpredictability, and terrifying simplicity.

Moving forward to 1763, the British Army attmped to use smallpox as a weapon against Native Americans at the Siege of Fort Pitt. In an attempt to spread the disease to the locals, the Brits presented blankets from a smallpox hospital as gifts.

Although we now know that this would be a relatively ineffective way to transmit smallpox, the intent was there.

During World War II, many of the parties involved looked into biological warfare with great interest. The Allies built facilities capable of mass producing anthrax spores, brucellosis, and botulism toxins. Thankfully, the war ended before they were used.

It was the Japanese who made the most use of biological weapons during World War II, as among other terrifyingly indiscriminate attacks, the Japanese Army Air Force dropped ceramic bombs full of fleas carrying the bubonic plague on Ningbo, China.

The following quote comes from a paper on the history of biological warfare.

[T]he Japanese army poisoned more than 1,000 water wells in Chinese villages to study cholera and typhus outbreaks. […] Some of the epidemics they caused persisted for years and continued to kill more than 30,000 people in 1947, long after the Japanese had surrendered.”

Dr. Friedrich Frischknecht, professor of integrative parasitology, Heidelberg University, Germany

The Centers for Disease Control and Prevention (CDC) define bioterrorism as “the intentional release of viruses, bacteria, or other germs that can sicken or kill people, livestock, or crops.”

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How likely is a bioterrorism attack today?

This can be achieved in a number of ways, such as: via aerosol sprays; in explosive devices; via food or water; or absorbed or injected into skin.

Because some pathogens are less robust than others, the type of pathogen used will define how it can be deployed.

Utilizing such weapons holds a certain appeal to terrorists; they have the potential to cause great harm, of course, but they are also fairly cheap to produce when compared with missiles or other more hi-tech equipment.

Also, they can be “detonated,” and, due to the long time that it takes for them to spread and take effect, there is plenty of time for the perpetrator to escape undetected.

Biological weapons can be difficult to control or predict in a battlefield situation, since there is a substantial risk that troops on both sides will be affected. However, if a terrorist is interested in attacking a distant target as a lone operant, bioterrorism carries much less risk to the person.


Experts believe that today, the most likely organism to be used in a bioterrorism attack would be Bacillus anthracis, the bacteria that causes anthrax.

It is widely found in nature, easily produced in the laboratory, and survives for a long time in the environment. Also, it is versatile and can be released in powders, sprays, water, or food.

Anthrax has been used before. In 2001, anthrax spores were sent through the United States postal system. In all, 22 people contracted anthrax — five of whom died. And, the guilty party was never caught.


Another potential agent of bioterrorism is smallpox, which, unlike anthrax, can spread from person to person. Smallpox is no longer a disease of concern in the natural world — because concerted vaccination efforts stamped it out — and the last naturally spread case occurred in 1977.

However, if someone were to gain access to the smallpox virus (it is still kept in two laboratories — one in the U.S. and one in Russia), it could be an effective weapon, spreading quickly and easily between people.


We have already mentioned the Tartars’ use of the plague, Yersinia pestis, hundreds of years ago, but some believe that it could be used in the modern world, too. Y. pestis is passed to humans through the bite of a flea that has fed on infected rodents.

Once a human is infected, the resulting disease can either develop into bubonic plague, which is difficult to transmit among humans and fairly easy to treat with antibiotics, or — if the infection spreads to the lungs — it becomes pneumonic plague, which develops rapidly and does not respond well to antibiotics.

A paper written on the plague and its potential for use in biological terrorism says:

Given the presence and availability of plague around the world, the capacity for mass production and aerosol dissemination, the high fatality rate of pneumonic plague, and the potential for rapid secondary spread, the potential use of plague as a biological weapon is of great concern.”

Dr. Stefan Riedel, Department of Pathology, Baylor University Medical Center, Dallas, TX


As a potentially severe and sometimes deadly gastrointestinal disease, cholera has the potential to be used in bioterrorism. It does not spread easily from person to person, so for it to be effective, it would need to be liberally added to a major water source.

In the past, the bacteria responsible for cholera, Vibrio cholerae, has been weaponized by the U.S., Japan, South Africa, and Iraq, among others.


Some consider tularemia, an infection caused by the Francisella tularensis bacterium, as a potential bioweapon. It causes fever, ulcerations, swelling of lymph glands, and, sometimes, pneumonia.

The bacterium can cause infection by entering through breaks in the skin or by being breathed into the lungs. It is particularly infectious, and only a very small number of organisms (as few as 10) need to enter the body to set off a serious bout of tularemia.

Studied by the Japanese during World War II and stockpiled by the U.S. in the 1960s, F. tularensis is hardy, capable of withstanding low temperatures in water, hay, decaying carcasses, and moist soil for many weeks.

According to the Johns Hopkins Center for Public Health Preparedness, “Aerosol dissemination of F. tularensis in a populated area would be expected to result in the abrupt onset of large numbers of cases of acute, non-specific, febrile illness beginning 3 to 5 days later […], with pleuropneumonitis developing in a significant proportion of cases.”

“Without antibiotic treatment, the clinical course could progress to respiratory failure, shock, and death.”

Those pathogens are an abbreviated selection, of course. Others considered to have potential as biological weapons include brucellosis, Q fever, monkeypox, arboviral encephalitides, viral hemorrhagic fevers, and staphylococcal enterotoxin B.

Although biological weapons are as old as the hills (if not older), modern technology brings new worries. Some experts are concerned about recent advances in gene editing technology.

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Could gene editing become the bioterrorist’s tool of choice?

When utilized for good, the latest tools can work wonders. However — as with most cutting-edge technology — there is always the potential for misuse.

A gene editing technology called CRISPR has set off alarm bells in the defense community; the technology allows researchers to edit genomes, thereby easily modifying DNA sequences to alter gene function.

In the right hands, this tool has the potential to correct genetic defects and treat disease. In the wrong hands, however, it has the potential for evil.

CRISPR technology is becoming cheaper to run and therefore more accessible to individuals bent on bioterrorism.

A report titled Worldwide Threat Assessment of the U.S. Intelligence Community, written by James Clapper, the director of National Intelligence, was published in February 2016. In it, gene editing features in a list of weapons of mass destruction and proliferation.

“Given the broad distribution, low cost, and accelerated pace of development of this dual-use technology,” he explains, “its deliberate or unintentional misuse might lead to far-reaching economic and national security implications.”

“Advances in genome editing in 2015,” he continues, “have compelled groups of high-profile U.S. and European biologists to question unregulated editing of the human germline (cells that are relevant for reproduction), which might create inheritable genetic changes.”

With future generations of CRISPR-like technology and an advanced knowledge of genetics, there would be no theoretical end to the misery that could be caused. There’s potential to create drug-resistant strains of diseases, for instance, or pesticide-protected bugs, capable of wiping out a country’s staple crop.

For now, however, other methods of bioterrorism are much easier and closer to hand, so this is likely to be of little concern for the foreseeable future.

In fact, to lighten the mood at the end of a somewhat heavy article, just remember that anyone who lives in the U.S. today is much more likely to be killed in an animal attack than a terrorist attack — biological or otherwise.