A prohibition signed by 189 countries sounds robust, yet the international ban on biological weapons has no independent inspection body capable of verifying compliance.
That structural weakness has taken on new urgency as artificial intelligence gives researchers, and potential bad actors, unprecedented power to analyze and manipulate dangerous pathogens.
In October 2026, MI5 Director General Ken McCallum warned publicly that AI tools could amplify the threat posed by biological weapons, raising particular alarm about risks from non-state actors.
His warning followed a September 2026 report by American AI company Anthropic, which revealed it had identified and blocked multiple attempts to misuse its Claude assistant for what appeared to be biological weapon-related research.
Those blocked attempts included grant applications for so-called “gain-of-function” research and projects investigating avian influenza variants selected for their potential transmissibility to mammals.
Anthropic acknowledged the difficulty of drawing firm lines, noting that such research can also serve legitimate medical prevention purposes, a tension experts describe as the dual-use problem.
The same laboratory equipment used to produce vaccines and life-saving medicines could, in theory, be repurposed for military biological research, making oversight extraordinarily difficult to implement.
Unlike chemical weapons, which cause harm through the immediate toxic effects of substances such as sarin, mustard gas, or chlorine, biological weapons work by triggering infectious disease that may take hours, days, or even weeks to manifest.
A further complication is that some pathogens can spread from person to person after initial deployment, making the ultimate scale of a biological attack almost impossible to predict in advance.
The World Health Organization and the UN Office for Disarmament Affairs define a biological weapon as the deliberate release of bacteria, viruses, fungi, or biological toxins to harm people, animals, or plants, with anthrax among the most notorious agents due to its spores’ ability to persist in the environment for extended periods.
These weapons are categorized alongside nuclear and chemical arms as weapons of mass destruction, yet their international control framework remains the weakest of the three.
The Biological Weapons Convention, which entered into force in 1975 and built upon the Geneva Protocol of 1925, requires signatories to destroy all stockpiles, production sites, and delivery systems, but relies almost entirely on voluntary reporting and good faith rather than on-site inspections.
By contrast, the Chemical Weapons Convention is enforced by the Organization for the Prohibition of Chemical Weapons, which holds the authority to conduct inspections and oversee the verified destruction of chemical stocks.
Governments have resisted creating an equivalent body for biological weapons, fearing that international inspectors could inadvertently expose sensitive commercial data from the pharmaceutical and biotechnology sectors.
The cost of that enforcement gap became starkly visible in the United States in late 2001, when letters containing anthrax spores were mailed to several recipients in the weeks following the September 11 attacks, infecting 22 people and killing five.
A biological attack can also evade early detection because an initial outbreak is often indistinguishable from a naturally occurring epidemic, requiring extensive investigation before deliberate release can be confirmed.
Historically, the weaponization of disease predates modern science, with documented cases ranging from the deliberate poisoning of water supplies to the medieval tactic of catapulting plague-ridden corpses over the walls of besieged cities, though historians debate how effective such methods actually were.
Nations that have not signed or ratified the 1975 Convention include Israel, Egypt, and Syria, leaving visible gaps even in the treaty’s formal reach.
As biotechnology accelerates and AI lowers the barrier to advanced pathogen research, pressure is mounting on governments and international institutions to finally close the verification gap that has left the world’s biological weapons ban largely dependent on trust.
