Part II, Biological Weapons. Biological Agents Biological agents are either disease causing organisms or toxins produced by a living organism. The disease causing organisms could be some type of bacteria, virus or rickettesia. All of which can be treated with antibiotics, while most toxins cannot.
Bacteria are single celled organisms in plants, animals and humans that can cause diseases.
Viruses are smaller than bacteria and live inside an individual host cell. Rickettesia are small cellular organisms that are smaller than bacteria but larger than a virus. They also live inside an individual host cell. Toxins are substances produced by living organisms including bacteria, plants and animals. They differ from chemical agents, in that most are not manmade.