What are biological agents?

• A. Substances used to decontaminate scenes.
• B. Organisms that cause disease, including viruses and bacteria.
• C. Environmental toxins.
• D. Nonpathogenic organisms.

Answer: (B)

Biological agents are living organisms or their derivatives that can cause disease or infection in people, animals, or plants. The most familiar examples are viruses and bacteria, which can multiply inside hosts and lead to illness. This definition is what makes the option describing disease-causing organisms the best choice, because it directly identifies what biological agents are in real-world safety and response contexts. The other descriptions refer to substances used for cleaning up exposures (decontaminants), chemical hazards (environmental toxins), or organisms that don’t cause disease (nonpathogenic organisms), none of which capture the disease-causing aspect at the heart of biological agents.