Bioterrorism is the intentional release of biological agents. Biological agents are organisms or toxins that can kill or disable people, livestock and crops. Biological events can either be accidental or intentional. Both types of events can make you sick. They may be naturally occurring or human-modified. The agents are typically found in nature, but they may be altered in a laboratory to increase their resistance to antibiotics, and ability to spread in the environment.
There are three basic groups of biological agents that could either accidentally or intentionally hurt someone: bacteria, viruses and toxins. Biological agents can be spread when they get sprayed into the air, with person-to-person contact, when animals are infected and then interact with people, or when food and water are contaminated. Terrorists use biological agents because they are often difficult to detect and illness onset may be delayed for hours to days increasing dispersal.