Military and political leaders have worried about large-scale biological warfare for more than a century. “Blight to destroy crops, Anthrax to slay horses and cattle, Plague to poison not armies only but whole districts—such are the lines along which military science is remorselessly advancing,” Winston Churchill lamented in 1925. But despite the deadly potential of biological weapons, their actual use remains rare and (mostly) small scale. Over the last several decades, most states have given up their programs. Today, no country is openly pursuing biological weapons.

Recent breakthroughs in gene editing have generated massive excitement, but they have also reenergized fears about weaponized pathogens. Using gene-editing tools, including a system known as CRISPR, scientists are now able to modify an organism’s DNA more efficiently, flexibly, and accurately than ever before. The full range of potential applications is hard to predict, but CRISPR makes it much easier for scientists to produce changes in how organisms operate.

Katherine Charlet
Katherine Charlet was the inaugural director of Carnegie’s Technology and International Affairs Program.
More >

These technologies offer vast potential for global good. Researchers are studying the use of new gene-editing techniques to fix deadly genetic mutations, create disease-resistant crops, and treat cancer. Top scientists at Harvard are pursuing medical applications once thought to be out of reach, such as age reversal and transplanting pig organs into humans. But it’s not hard to imagine how gene-editing technologies could be misused. Some fear that terrorists with even moderate capabilities could develop deadlier pathogens. And laboratories, appealing to parents’ instincts to offer advantages to their children, could modify embryos in ways that cross ethical boundaries.

One of the most worrisome questions today is whether advances in biotechnology could tempt states to revive their old biological weapons programs or start new ones. Such an outcome would drastically undermine the progress of the last several decades. A revitalization of state biological weapons programs could trigger new conflicts or rekindle old arms races, destabilizing the international order.

Faced with extremes of promise and peril, policymakers must proceed with a sense of perspective. Fear-mongering or overregulation could undercut the almost unimaginable benefits of the biotechnology revolution. But failing to anticipate and manage the significant risks, including the resurgence of state biological weapons programs, would be equally problematic.


Understanding the risks that biological weapons pose today requires a closer look at how states have historically weighed their benefits and drawbacks. Since 1945, only six countries have publicly admitted developing biological weapons, although sufficient evidence exists to suspect a dozen or more. As the biological warfare expert W. Seth Carus has pointed out, states have pursued these weapons for a number of different reasons.

Between 1942 and 1969, the United States developed a highly advanced biological weapons program, which was capable of large-scale lethality. Initially, this program was designed as a deterrent, but American researchers also came to value the flexibility of biological weapons, which could temporarily sicken or disable people rather than kill them. During the Cold War, the Soviets also conceived of a range of strategic and operational uses for biological weapons. In addition to lethal uses, for example, they explored targeting agriculture to damage an enemy’s food stocks, economy, and morale. Stalin even considered using the organism that causes plague to assassinate Marshal Tito, then the president of Yugoslavia.

The materials needed to develop biological weapons are easy to access and relatively cheap. Many pathogens, such as the one that causes anthrax, don’t need to be developed in a lab; they can be found in nature. And states pursuing biological weapons can readily obtain the necessary equipment, which is the same as what is needed for medical or defense research. Biological weapons also offer deniability: attacks can look like natural outbreaks, and they are difficult to attribute.

But in practice, biological weapons also pose tactical and technical challenges, which led many decision-makers to question their overall value. From a tactical perspective, the time lag between exposure and symptoms has limited the utility of biological weapons on a battlefield. And target populations can protect themselves with vaccines and other countermeasures. Launching a successful large-scale attack is also difficult. Unpredictable winds, changing terrain, or incorrect dosage could all lead to failure. According to Carus, the United States and the Soviet Union are the only two countries believed to have overcome such challenges enough to be capable of using aerosol releases to reliably disseminate biological weapons over a large area.

Indeed, a significant problem with biological weapons has been the prospect that the agent could blow back on the users, infecting the attacking country’s own soldiers and citizens as well as the enemy’s. In the late 1930s and early 1940s, Japan undertook the largest-scale use of biological weapons in modern times, conducting both small attacks and larger campaigns in China. During one campaign, the Japanese dropped plague-infected fleas from aircraft onto Chinese targets and spread organisms responsible for other diseases in water and rice fields. Estimates of the Chinese death toll from the Japanese biological weapons attacks are debated and unverifiable, but they range from tens of thousands to several hundred thousand. In the process, however, it is thought that these attacks also killed well over a thousand Japanese.

These tactical and technical hurdles are not insurmountable, of course. But they have contributed to the lack of any known state use of biological weapons for the last several decades and to a broader trend of states voluntarily ending their programs. For example, disappointing test results and disenchantment with the deterrent power of biological weapons contributed to the decision by the British to deprioritize their program and stop developing offensive capabilities in the late 1950s. Although the U.S. program was more sophisticated than the British one, U.S. President Richard Nixon still terminated it in 1969, in part because he was unsure if it contributed to national security. The question today is whether new biotechnological applications might loosen those constraints.


Gene-editing techniques such as CRISPR could make biological weapons more deadly. Nations could develop novel or modified pathogens that would spread more quickly, infect more people, cause more severe sickness, or resist treatment more fully. Equipment needed for wide-area dispersal may become less necessary, for example, if a pathogen can be engineered to spread faster on its own. Whether that potential is tantalizing enough to convince countries to revitalize or initiate biological weapons programs is uncertain. These kinds of modifications have long been possible, just harder, using traditional genetic engineering techniques. But there are worrying signs that some leaders sense a new opportunity. In 2012, for example, Russian President Vladimir Putin intimated to his defense minister that he should plan to develop weapons based on new principles, including genetics.

Another concern is that gene editing may make it easier to carry out targeted assassinations. Conceivably, a government might edit the genes of a deadly virus so that it would affect only a single target based on his or her genetic code. This capability does not yet exist, but it might become possible with time and effort. Nonetheless, as the biosecurity expert Gigi Gronvall has noted, given the prevalence of far easier methods of assassination, states may decide that developing and testing such a weapon is not worth the time, effort, and cost.

A related fear is that advances in gene editing could allow scientists to develop biological weapons capable of discriminating among target populations based on ethnic, racial, or other genetically defined characteristics. According to Gronvall, these so-called ethnic weapons would be tricky to design and test, and any target population would likely have considerable overlap with nontarget populations. Still, the world is only in the early stages of the biotechnology revolution, and biological weapons have been used in ethnic and racial conflicts before. In the 1970s, for example, Rhodesia’s intelligence agency introduced cholera into wells in areas held by black nationalist guerillas. And in 1981, the apartheid government of South Africa launched Project Coast, which is believed to have looked into biological means to assassinate opponents. According to some accounts, researchers with Project Coast also discussed plans to selectively administer an antifertility vaccine to black women. These examples give reason to monitor the threat of targeted biological weapons.

Some observers argue that gene editing could make it easier to develop or use biological weapons clandestinely, thus reducing the risk of international disapprobation. But maintaining a secret biological weapons program has never been particularly difficult. The equipment and agents required also have legitimate uses, and the challenges of international oversight mean that the odds of getting caught are low. It is unlikely that new technologies would change this in any fundamental way.

Concerns that gene editing will make biological weapons so cheap that countries reassess their strategic value are also overstated. CRISPR does make gene editing less expensive; in 2014, a scientist at Vanderbilt University noted that an activity that used to take 18 months and cost about $20,000 took only three weeks and cost about $3,000. The expense can only have fallen in the years since this estimate was made. But biological weapons are already cheaper than alternatives such as nuclear weapons. And although gene editing lowers the cost of developing a deadly pathogen, it does little to reduce the price tag on the many other steps involved, such as weaponization, manufacturing, and delivery.

Considering all of this, one particular concern emerges. The combined factors of lower cost, easier access, and greater effectiveness might not be enough to sway major powers, but they may incentivize rogue and small states to reconsider the marginal utility of investing in biological weapons. As a result, any strategy to address the risk of genetically edited biological weapons must take into account a broad range of state types, not just the major powers. Still, it’s important to put the threat in perspective: geneediting advancements need not change the basic calculus to the extent that some fear.


Major disincentives to the use of biological weapons already exist, and they can be strengthened to prevent countries from revitalizing or starting biological weapons programs. This is not an excuse for complacency; countries will need to reinforce and update the existing protections in light of new capabilities. Still, the norms and incentives against the use of traditional biological weapons should buy time and space for the international community to put new measures in place.

The vast majority of states—180 of them—are parties to the 1972 Biological Weapons Convention, which bans the development, stockpiling, acquisition, retention, and production of biological agents for nonpeaceful purposes. Although the treaty is often criticized for its lack of a meaningful enforcement mechanism, it has helped establish a global norm that using biological weapons is immoral and unacceptable. Although such norms may not constrain the worst actors’ behavior, they do provide the rationale and motivation for the rest of the world to punish violators.

Today, any state that used biological weapons, genetically edited or otherwise, would meet severe reprisal from other states seeking to defend the norm of nonuse. Breaking the status quo, even on a small scale, would turn any country into a pariah. Few would be willing to take that risk, and those most likely to do so, such as North Korea or Syria, already face sanctions and military containment. Were either of these states to use biological weapons, the United States and its allies would almost certainly respond with force.

Becoming a “first misuser” of a genetically edited biological weapon could also prevent a state from enjoying the positive applications of the new technologies. Researchers, businesses, and governments worldwide hope to take advantage of advanced biotechnologies in medicine, agriculture, and manufacturing. Countries discovered to be misusing such technologies could end up undermining their own businesses and research institutions and cutting their citizens off from the benefits discovered by others. Of course, if a country were to find that it profits little from the new technologies, then this disincentive would be lessened— one reason why the purveyors of new biotechnological applications should strive to make them affordable and widely available.

Ultimately, the power of these disincentives hinges on the ability to determine that an attack has occurred and to identify its source. For now, investigators looking at a pathogen in the aftermath of an attack would not necessarily be able to tell if gene-editing techniques had been used. Although plausible deniability could lower a state’s inhibitions, it probably would not eliminate them altogether. The perpetrator of an attack might still be uncovered through other means, such as espionage.

Of course, individual terrorists and groups such as the Islamic State, or ISIS, do not feel bound by international norms. Indeed, gene-editing advancements do increase the risk that such actors could use biological weapons. But strong international norms are still useful, because they motivate the rest of the world to prevent and punish violations. The possible revitalization of state programs requires explicit attention because it is a more multidimensional threat. Not only could state programs produce deadly weapons, but the existence or use of the resulting weapons could trigger conflict, escalation, arms races, and other destabilizing events.


The current system does not eliminate the risk that a state could see new value in biological weapons, but it is enough to give any country pause. That means that the international community still has time to reinforce the current norms against all types of biological weapons and decrease the perceived benefits of genetically edited ones.

First, countries must strengthen the Biological Weapons Convention. Since 1986, state parties to the convention have affirmed that the treaty’s prohibitions apply to new scientific and technological developments. The prohibitions likewise apply regardless of the origin or method of production of a biological agent. In December 2017, state parties agreed to initiate a series of discussions on the risks of new technologies. These are important foundations, but more steps are required.

The five permanent members of the UN Security Council should invite other states to join them in making a strong statement that emphasizes the enormous positive potential of synthetic biology techniques, including gene editing, and reiterates their firm commitment to use such techniques for nonhostile purposes only. Reinforcing the positive potential of these new technologies could strengthen current norms by broadening awareness of what might be lost if a violation occurs.

Above all, countries must strengthen their ability to detect and respond to biological attacks. If gene editing can help create pathogens that spread more widely and quickly, then nations must detect outbreaks sooner, wherever they originate. If gene editing enables novel pathogens, then nations need the capability to rapidly create novel countermeasures. If gene editing allows for more clandestine uses of biological weapons, then nations require better techniques for determining their origin. Such improved capabilities would act as a deterrent by denying perpetrators the devastation they might hope to achieve. Fortunately, they are exactly what is needed to safeguard global health more generally.

Yet governments are not moving in the right direction. A February report by the Blue Ribbon Study Panel on Biodefense warned that U.S. spending remains out of sync with actual threats. Outbreak response—such as the $5.4 billion spent on Ebola in 2014—is essential, but resources should also be spent on programs that might prevent outbreaks in the first place. The latest White House budget cuts funding for the Centers for Disease Control and Prevention’s preparedness and response programs by $20 million and its programs for emerging infectious diseases by $60 million. Instead, Washington and other governments should be protecting and coordinating their biological defense, prevention, and preparedness budgets for maximum effectiveness. Strategically applied resources and strong leadership would save lives by enabling quick responses to outbreaks, thus limiting the impact of disease—even if no one ever conducted a purposeful attack.

To make the most of limited resources, governments and biosecurity experts should improve their coordination by developing an international biological security strategy. Such a strategy would mobilize national and international bodies to detect harmful new diseases or health anomalies in human populations, agriculture, and the environment and to share information about them. It would also marshal financial and institutional resources to quickly utilize gene editing and other new techniques to produce countermeasures against harmful, and potentially novel, pathogens. The elements of such a strategy are not new. As in so many other fields, what is needed is sustained, high-level leadership to promote and implement them.

The United States can be a leader in these efforts, given its broad influence and technical know-how. None of these proposals would require new regulations that would stifle American business or innovation. Nor would they prevent militaries from conducting lawful operations. Some steps would cost money, but the price tag would pale in comparison to the damage caused by a well-executed biological attack or even a large, naturally occurring outbreak. If the United States is not willing to lead, China has increased its investment in global health over the last decade and might step into the void.

In seeking to prevent the use of biological weapons, governments, businesses, and scientists must arm themselves with equal parts fear and confidence, urgency and pragmatism. Given recent technological advancements, the consequences of a return to an era of states with biological weapons programs would be devastating. But a sound strategy to keep the disincentives strong can keep that possibility in the realm of fiction.

This article was originally published by Foreign Affairs.