What are the two categories of biological agents?

• A. Pathogens and toxins
• B. Bacteria and viruses
• C. Cells and tissues
• D. Fungi and algae

Answer: (A)

Biological agents come in two broad categories: living organisms that can cause disease (pathogens) and toxic substances produced by living organisms that can harm people (toxins). Pathogens are the organisms capable of infection and illness, such as certain bacteria, viruses, fungi, and parasites. Toxins, on the other hand, are poisonous substances that can cause harm without requiring infection—for example, botulinum toxin produced by bacteria. This distinction matters for response: preventing or treating infections targets pathogens and transmission, while preventing exposure and neutralizing toxins target the toxic substances themselves. The other options mix up types (bacteria and viruses are specific pathogens, not the two categories), or refer to materials or organisms that aren’t themselves the defined categories of biological agents.