Biological warfare dates back to antiquity, but it occurs throughout history. The deliberate poisoning of food and water with infectious material, the use of micro-organisms, toxins or animals, living or dead, in a weapon system and the use of biologically inoculated fabrics are among the most common uses of biological agents.
The 20th century World Wars had a huge impact on the development of biological agents. Throughout the First World War, the German army had a programme to weaponise anthrax, glanders, cholera, and a wheat fungus. During World War II, Japanese forces operated a secret biological warfare research facility that included experiments on prisoners. The United States also had a programme investigating the use of anthrax and botulinum toxin as biological weapons, whereas the British tested anthrax bombs and prepared and stockpiled anthrax-laced cattle cakes. The United States continued their research on various offensive biological weapons during the 1950s and 1960s. Today, some countries are believed to still run their own biological weapons research programmes. Terrorist organisations and individuals may find the use of biological agents an attractive option, because they will spread fear and disrupt society. The greatest threat may come from organisations that are well funded and possibly state-supported. These are the most likely to gain access to scientific expertise to create, store and weaponise biological agents.
Most biological warfare agents are ubiquitous in the natural environment, occurring in water, soil, plants and animals. Most agents reproduce rapidly and require minimal resources for preservation. The most dangerous biological agents are easy to disperse, stable and lethal even in small doses. They spread easily from person to person or can be aerosolised as an effective method of delivery. There are four kinds of biological warfare agents: bacteria, viruses, rickettsiae and toxins.