Biological weapons are prohibited under international law. But new developments in biotech and AI are a cause for concern. DW addresses some of the most important questions about their history, risks, and control.

Artificial intelligence could potentially be misused to develop biological weapons. This may sound like science fiction, but scientists, security services, and international organizations are all looking at how to deal with this scenario .

Pathogens can be analyzed and altered with ever greater precision thanks to ongoing developments in biotechnology. Meanwhile, AI is able to evaluate vast quantities of data at astonishing speeds. As a result, experts are warning that, in the long term, modern technologies could also be misused to develop biological weapons.

Security services are concerned. In October 2026, Ken McCallum, head of the British domestic intelligence service MI5, warned that artificial intelligence could increase the risk from existing, or new, biological weapons – including from non-state actors . Fine line between valid research and misuse A report by the American AI company Anthropic in September 2026 highlights the topicality of the debate. Anthropic said it had identified and blocked numerous attempts to use its AI assistant Claude in connection with possible biological weapon research.

The report said these attempts included grant applications for so-called "gain-of-function" research, as well as projects to research avian influenza variants that were potentially the most transmissible to mammals.

At the same time, Anthropic stressed that, although it could have a military application, such research could also relate to medical prevention. The difficulty in distinguishing between legitimate science and its possible misuse is one of the biggest problems in terms of the control of modern biotechnologies. What are biological weapons?

Concerns about biological weapons are by no means new. Many pathogens — bacteria, viruses, fungi, and certain biological toxins — have the potential for weaponization. Familiar diseases include plague , smallpox, and botulinum toxin, but anthrax is one of the most notorious biological agents. Its resistant spores can survive a long time in the environment, and it has also been the focus of research by state biological weapons programs. Melting ice brings new dangers To view this video please enable JavaScript, and The World Health Organization (WHO) and the United Nations Office for Disarmament Affairs define a biological weapon as the targeted release of such biological substances for the purpose of injuring people, animals, or plants.

A biological weapon usually has two components: The biological substance itself, and a system for disseminating it. Experts refer to these as the "agent," such as a virus or bacterium, and the "delivery mechanism." Examples of the latter include missiles, spraying systems, and contaminated food.

Biological weapons belong to the so-called ABC weapons, alongside atomic (nuclear) and chemical weapons. They are often also counted as weapons of mass destruction. How do they differ from chemical weapons?

Biological and chemical weapons differ in their mode of operation. Chemical weapons injure people through the toxic effects of chemical substances such as sarin or mustard gas. They will often take effect within minutes, or even seconds. Examples of the use of chemical weapons are the gas attacks in World War I, which involved chlorine gas, and later mustard gas; and the deployment of the nerve gas sarin in the Syrian civil war and by Saddam Hussein in Iraq .

Biological weapons, on the other hand, cause infectious disease. The effects become apparent only hours, days, or even weeks after they have been deployed. Some pathogens are also capable of spreading from person to person, meaning that the outcome is difficult to predict.

To summarize: Chemical weapons kill or injure through immediate toxicity, whereas biological weapons cause diseases. The possibility of human-to-human transmission makes the effect of a biological weapon particularly hard to calculate. Are biological weapons subject to a worldwide ban?

Biological weapons are prohibited under international law. The first Biological Weapons Convention (BWC) came into force in 1975. This prohibits the development, stockpiling, acquisition, retention, production, and transfer of biological and toxin-based weapons.

The Convention, which has been ratified by 189 countries, can be seen as a development of the Geneva Protocol of 1925, which banned the use of biological weapons as a method of warfare. Only a few countries have not signed the agreement , or have signed but not ratified it, including Israel, Egypt, and Syria. All those who have acceded to the Convention have also committed themselves to destroying all stocks , production sites, and means of conveyance.

Chemical weapons are also internationally banned, but their control is seen as much more highly developed. The Chemical Weapons Convention is implemented by the Organization for the Prohibition of Chemical Weapons ( OPCW ), which can carry out inspections and oversee the destruction of chemical weapons stocks.

There is still no comparable system for controlling biological weapons . States fear that inspection could expose sensitive research data pertaining to medicine, biotechnology, or the pharmaceutical industry. This is why the control of biological weapons relies to a great extent on transparency, voluntary reporting, and good faith.

One of the best-known examples of why the ban on biological weapons is insufficient on its own to prevent their use occurred in the United States in 2001. A few weeks after the attacks of September 11, several people received letters containing anthrax spores. 22 were infected, and five died.

Million-dollar reward: In 2001, anthrax was sent by post to several prominent Americans in an act of domestic terrorismImage: USPS/dpa/picture alliance Why are biological weapons so hard to expose and control?

Finding biological weapons programs is much harder than controlling the production of nuclear or chemical weapons. Many technologies that could be used to develop biological weapons also have civilian applications. The same laboratory equipment used to develop vaccines and medicines could, in theory, also be used for military research.

Experts refer to this as the problem of dual use. Research can be done for peaceful medical purposes and, at the same time, have a military application.

Furthermore, a biological attack can initially look like a natural outbreak of disease. It is often only possible after extensive investigation to establish whether a pathogen was deliberately released or occurred naturally .

Perhaps that is also why biological weapons have been deployed at various times throughout history. Historical reports range from the poisoning of wells to catapulting the corpses of plague victims over the walls of a besieged town. The effectiveness of these methods is, however, disputed. This article has been translated from German.