The COVID-19 pandemic has been a wake-up call in terms of the security, economic and public health devastation infectious diseases can cause.

In addition to the mass death and global disruption caused by the virus, and the indirect security consequences of those dynamics, there have also been direct consequences for security, including the sidelining of aircraft carriers, infection of heads of state and the quarantining of military leaders central to chains of command. For those tasked with addressing biological weapons threats, these effects continue to raise questions of whether some actors could be more likely to consider deliberately weaponizing diseases.

Though much work remains to be done, the technologies and capabilities now being deployed for pandemic responses are giving rise to an historical opportunity for the nation: It is time to end the U.S. policy of using nuclear weapons to deter biological weapon threats.

Today, the U.S. nuclear posture positions nuclear weapons as a leading means of deterring strategic-level biological weapons activities. As the 2018 Nuclear Posture Review described, the roles of U.S. nuclear forces currently include acting as a “hedge against the potential rapid growth or emergence of nuclear and non-nuclear strategic threats, including chemical, biological, cyber, and large-scale conventional aggression.”

This creates several problems. One is raising miscalculation risks in complex security environments, in particular because of the challenge of understanding whether a disease outbreak arises naturally, by accident or from a deliberate attack. Consider the continuing confusion regarding COVID-19 nearly two years after its emergence. The U.S. intelligence community still cannot determine with high certainty whether it emerged naturally or via a lab accident. China, Iran, Russia and others have accused the United States of creating the culprit virus as a biological weapon.

How would this nuclear policy be applied if such confusion and disinformation occurred regarding a severe disease outbreak in a conflict setting or in highly tense circumstances? And would restraint regarding such a step contribute to the nation’s leaders not taking seriously enough the question of whether a biological weapon was used? The ambiguity of application of this nuclear weapons policy is seen as a tool to maintain flexibility during a crisis and avoid driving escalatory behavior. Yet it brings serious risks as well.

Further, deterring biological weapons with nuclear weapons may be ineffective. Deterrence by punishment requires that threats be credible and that the targeted entity believes the threatened action (in this case a nuclear strike) would be carried out. This is not likely to be the case. As the United States has continued this nuclear policy, several chemical weapons attacks have been carried out at targeted scales. Numerous significant cyber attacks and intrusions have been undertaken as well. For biological weapons, the Department of State’s 2021 arms control treaty compliance report determined North Korea and Russia already have offensive biological weapons programs. It also registered continuing concerns that China and Iran have engaged in dual-use activities that extend beyond what is allowed by the Biological Weapons Convention.

These types of threats will always remain in some form. Yet the United States now has potentially promising, different pathways to addressing them that simultaneously reduce nuclear risks while strengthening nuclear deterrence.

President Biden has already indicated the foundation of such a path: a “sole purpose” policy for U.S. nuclear weapons. As he wrote in Foreign Affairs in 2020: “I believe that the sole purpose of the U.S. nuclear arsenal should be deterring — and, if necessary, retaliating against — a nuclear attack. As president, I will work to put that belief into practice, in consultation with the U.S. military and U.S. allies.”

This is a sound step toward reducing nuclear risks. Yet the United States can’t halt its efforts to deter biological threats.

The solution is to shift toward a strategy of deterrence by denial for biological weapons threats. Put simply, this would mean creating systems to ensure the nation can rob offensive biological weapons of their intended mass effects. Just as this theory has been applied with regard to conventional armed forces and postures, the aim is to ensure that an adversary will not carry out an attack knowing that a) it would likely be ineffective, and b) that the consequences would be severe. The threat of punishment with conventional weapons would remain intact as part of a deterrence by denial approach.

As RAND expert Michael Mazarr described in 2018, “Most classic studies suggest that denial strategies are inherently more reliable than punishment strategies. Steps taken to deny, such as placing significant military capabilities directly in the path of an aggressor, speak loudly and clearly.”

In past decades, the technologies and tools needed for a denial approach to biological weapons were envisioned, but not yet advanced enough or deployable at scale. Today, that has changed, including due to significant Department of Defense efforts.

Key requirements for denying bioweapons effects would include catching an introduced infectious disease quickly, characterizing it fast and spreading that information to responders, using genetic-level information to rapidly develop diagnostic tests and medical countermeasures, and keeping personnel protected as best as possible while these steps are taken to quash transmission. The emphasis on each step may change based on the characteristics of specific pathogens.

Scientists and technologists in the United States and globally have advanced such technologies at an incredible pace in the past several years. Building on basic science breakthroughs, biotech tools are now married to advanced analytics and robotics to make detection and response capabilities better and faster than ever. This includes past DoD biodefense efforts that contributed to the mRNA platforms that were first used at mass scale for COVID-19 vaccines.

Creating systems for a deterrence by denial strategy for biological weapons will take time, but now is the time to start. The United States has fumbled many times in the first-ever crisis deployment of many of the technologies required. However, such deployment is already occurring around the nation. This can be sustained and expanded upon, and applied to military bases and other strategic locations around the world.

The U.S. should include a sole-purpose doctrine in the forthcoming Nuclear Posture Review, sustain over time the investments in addressing biological threats that have brought new technologies into use, and formally adopt plans to move toward a deterrence by denial strategy for biological weapon threats. Such policies will make the U.S. nuclear deterrent even more credible and show U.S. leadership in reducing nuclear risks.

Christine Parthemore is the chief executive officer of the Council on Strategic Risks, where she also leads the Janne E. Nolan Center on Strategic Weapons. She was formerly senior advisor to the Assistant Secretary of Defense for Nuclear, Chemical and Biological Defense Programs.

Andy Weber is a senior fellow at the Council on Strategic Risks. His decades of U.S. government service included five-and-a-half years as the Assistant Secretary of Defense for Nuclear, Chemical and Biological Defense Programs.

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