What are biological weapons?

A biological weapon is any weapon that uses a disease-causing agent to cause harm to its intended target, whether human, animal or plant. A biological weapon can take many forms.

In ancient times, the type and use of biological weapons were primitive and opportunistic such as adversaries poisoning wells with animal corpses or catapulting diseased corpses over walls during sieges. However, with scientific advances and new understandings of how disease works, biological weapons in modern times became more sophisticated and were used in large scale for the first time during World War Two.

Biological weapons have since been banned by the international community in 1972 by the Biological Weapons Convention (BWC), but the threat of the use of biological weapons has since evolved from mainly states to so-called non-state actors (such as terrorist groups).

Today, the threat posed by biological weapons is often characterised as a low-probability, high consequence event but attempts by non-state actors to acquire or develop these weapons has led to international concern and increased efforts to strengthen biosecurity measures to ensure that biological weapons are never used again.

The effects of the use of a biological weapon can vary widely depending upon the agent used, which makes biological weapons very versatile, with the potential to be used in a wide-scale attack, or on a more limited basis for activities such as assassination, or for incapacitation rather than death. The ongoing COVID-19 pandemic could be used to demonstrate the widespread death and disruption caused by even an agent with low lethality, but high transmissibility.